2018/11/15

The Months through the Years

The title of today's post is not great, but we're going to be looking at how the temperatures for each month of the year have changed since records began. And thus: "The Months through the Years."

It goes back to this chart, which we saw last month in the October Review / November Preview:


There are quite a few things going on here:

  • The average Daily Mean temperatures (average of the Highs & Lows) for each October are the orange & blue bars. October 2018 ranked as the 92nd warmest since 1880.
  • The average Daily Low temperatures are the blue line - 2018 ranked 86th.
  • The average Daily High temperatures are the orange line - 2018 ranked 89th.

At the end of this animation the 10-Year Averages for the Low, Mean, and High appear as dotted, red lines. Those averages show how temperatures have changed over time, and they are what we're going to be talking about today. For October the average Low has risen from about -2°C to +1°C, but the average High has actually fallen from 12°C to 10°C. That last part seems weird.

Let's get started with a quick recap of Edmonton's temperature history:


Warm Years

We use this chart quite often. It shows how the average temperature for each year compares to the 20th century average. Back in the 1880s the temperatures here were 1°C or 2°C colder than the 20th century average, but since about 1975 most of our years have been 1°C or 2°C warmer than the 20th century average.

The numbers in this chart are for an entire year - they are the average of the Highs & Lows for all 365.25 days. But when we break that down a bit we will see that some parts of the year have changed more than others.


Warm Months

We've used this chart in the past too, and it shows how warm each month is, compared to the 20th century average for that month. This lets us see 20 years at a time, and over on the far right is the average for those 20 years. As this animation cycles through from the 1880's to today we can see how that average has changed from colder (blue) to warm (orange).


To make things simpler, here is the first slide of that animation which covers 1880-1899.

130+ years ago there were some warm months - notably January 1889 was 8°C warmer than the 20th century average, and November 1890 was 7°C above. But there were also some really cold months, with December 1880, January 1886, February 1887, and November 1896 averaging 11-14°C below the 20th century average.

When we look at the "20-Year Average Difference" column on the far right we can see that for this time period all twelve months of the year were below the 20th century average. January & February were the most below at -2.3°C and -3.1°C, whereas April & December were both only a little bit below at -0.3°C.


And in comparison here we have 1999-2018. There are still some blue bubbles here for cold months, with the most below-average month being March 2002 at -7°C. But just generally there is a lot more orange on this chart than what we saw for 1880-1899.

Looking at the "20-Year Average Difference" again:
  • The late-winter months of January & February have seen big changes in recent years, averaging 4.3°C and 2.4°C warmer than their 20th century average.
  • The early-winter months of November & December are only 1°C and 1.2°C warmer, which is about the same change that the summer months of June-September have seen. 
  • The shoulder-season months of April & October have actually been a little bit cooler than the 20th century average.

Even with plenty of variation year-to-year and month-to-month, January and February are where we've seen the most consistent and the largest changes. From the 1880's to today January's average temperature has increased by 6.6°C and February's has increased by 5.5°C. The next largest is March with only a 2.3°C change.

For this chart we are using the Monthly average of the Daily Mean temperature, which is the average of the Daily Highs & Lows. Next we are going to split the Highs & Lows up to see how they behave separately.


Monthly Lows

This chart cycles through the average Low temperature for each month of the year, with the history going back to 1880. The dotted red line is a standard best-fit trendline.

For all 12 months of the year the Low temperatures are trending upwards, although there is a lot of variation:

Monthly Average Low Temperatures





1880s
2010s
Change/Century
January
-21°C
-15°C
5.3°C
February
-19°C
-12°C
5.5°C
March
-12°C
-7°C
3.8°C
April
-3°C
0°C
1.7°C
May
3°C
6°C
2.5°C
June
7°C
11°C
3.2°C
July
9°C
13°C
3.3°C
August
8°C
12°C
3.3°C
September
3°C
7°C
3.1°C
October
-2°C
1°C
1.9°C
November
-10°C
-7°C
1.8°C
December
-16°C
-13°C
1.5°C

We don't normally use tables at Edmonton Weather Nerdery, but it's probably the easiest way to talk about this.

The Lows for January & February have changed a lot, trending upwards at more than 5°C per 100 years. March and the summer months have all increased at around the 3°C range. And then April and October-November have been more sedate, averaging 1.5°C-1.9°C per century.

The slopes of the various trendlines in this chart really make the differences between the months apparent. But normally we try not to use trendlines, because they imply that you can extrapolate into the future, even if that might not be appropriate. As an alternative to the trendlines, here is a different approach:


This chart is not as pretty unfortunately, but this uses the 10-Year average Low for each month instead of trendlines.

It tells a similar story to what we just saw above, albeit this time in a more wobbly fashion: January & February have increased a lot, May-September have a visible upward trend, and the rest of the months are a little flat-ish.

We've looked at the Daily Mean temperatures and the Daily Low temperatures, and so now all that's left is:


Monthly Highs

In this chart we've moved on from the Lows to the Highs, and the thing to notice here is that not all of the trendlines are sloped upwards:

Monthly Average High Temperatures





1880s
2010s
Change/Century
January
-10°C
-6°C
3.1°C
February
-7°C
-3°C
3.0°C
March
1°C
1°C
0.3°C
April
11°C
10°C
-1.0°C
May
18°C
18°C
-0.3°C
June
21°C
21°C
0°C
July
23°C
23°C
0.1°C
August
22°C
22°C
0.3°C
September
17°C
17°C
0.3°C
October
11°C
10°C
-0.7°C
November
1°C
1°C
-0.3°C
December
-6°C
-6°C
0.1°C

Again, January & February have had the biggest changes with average High temperatures increasing by about 3°C per century. The summer months have also trended upwards a little bit. But for the shoulder-season months the average Highs have actually fallen by -1°C for April and -0.7°C for October.

(if you've noticed that the numbers in these two tables don't add up to the bubblechart that we started with, there are two reasons for that: 1) the bubblechart used a 20-Year window while the tables use 10-Years; and 2) the tables use the best-fit line which isn't a perfect match to the measured data.)

Switching from trendlines to 10-Year averages again:


And this is similar again, with the Highs for January & February noticeably increasing, while the rest of the months look pretty flat.


The Yearly Rollercoaster

This is another way to look at things.

In this chart the blue and orange background is the range of our yearly Low temperature rollercoaster, for 1996-2018. The white line running through the middle is the recent average Low for each day of the year. The red line that appears is the average Low for 1880-1899.

For almost the entire year the red 1880-1899 line is shifted down from the white recent line, with really large gaps in late-January, early-February, and late-November. But for a few parts of the year - early-March, mid-April, late-November and early-December - the historic average Lows are very close to modern temperatures.


When we switch this chart to compare 1880-1899 average Highs the differences are less clear.

Again, there is a big gap between the red & white lines in late-January and early-February, where the High temperatures today really are 5°C warmer than they used to be. But for the rest of the year the lines are very close to one another. In April the lines look about even, but for October the red historic line is noticeably above the white modern line.


The Shoulder Season

So lets take a closer look at April & October:

April
October

With both April & October the Lows have increased by about as much as the Highs have decreased.

Those two months have something else in common:


On the yearly temperature rollercoaster April and October are mirror-images of each other. They are the two months where the temperatures are changing the fastest - from winter into spring, and from fall into winter.

But why have the average Highs nudged down over the years? No idea. That's outside the scope of mere weather nerdery, and it would need to be left to the real climate scientists out there.


December vs. January

We're going to finish today by taking a look at two neighbouring months who haven't been following the same path.

December

December's temperatures haven't changed very much over they years. The average Daily mean has hovered around -10°C, with the average High around -6°C or -7°C, and the average Low warming up a bit from -16°C to around -13°C. 

January

January is a different story, with the Highs, the Lows, and the resulting Daily Means all jumping up by more than 5°C.

And that means that January is no longer Edmonton's coldest month:


January used to be Edmonton's coldest month by far, with average Highs 5°C colder than February & December, and Lows 4°C below February and 5°C below December.

But because in recent year January & February have both warmed up so much they've passed December, putting it in coldest-spot for both Highs & Lows. The fact that our winter bottoms-out in December is something that we saw in Are we there (the middle of winter) yet?


Summary

In previous posts we have seen that Edmonton's recorded temperatures have been warmer recently than they were a century ago. We've also looked at nearby rural stations and to other Canadian cities, and have seen a similar pattern.

When we dig deeper into Edmonton's temperatures we see that the changes have been concentrated in January & February, with large increases in both the Highs and the Lows. The summer months and November & December have seen small increases to the average Lows, but the average Highs have been relatively unchanged. And for the shoulder-season months of April & October the average Lows have also increased a bit, but that has been offset by a decrease in the average Highs for those months.

And in general all of that goes back to something that we saw in one of Edmonton Weather Nerdery's earliest posts: Edmonton might not be getting much warmer, but it has been getting less cold.

2018/10/31

October Review / November Preview

October ended pretty nicely, but it didn't start out that way. Let's take a look back:

High Temperatures

Last month we talked about how September 2018 was one of the coldest Septembers ever recorded in Edmonton. And that coldsnap dragged on for another two weeks into October.

But then on October 14th our temperatures finally shot up above average again, for the first time since September 7th, more than a month earlier. Then we broke an all-time record on the 17th at 24.7°C. And we finished the month just a little bit warmer than average...although still well above what we'd seen for a lot of September.


Looking at the numbers, the average High of 10°C was just a little bit on the cooler side of things. Recent years have ranged from 2015 at 14.3°C down to 2016 at 5.7°C.

We had 1 day which hit 20°C, when about 1/3 of the time we don't get any in October. We only had 5 days which hit 15°C, which is more than a year like 2016 with 0, but less than 2014 with 14. And we had 2 Highs below freezing, which is unusual, but not impossible. The last time that we had a High below freezing in October was in 2013, but the year before that October 2012 had 10 of them.


Low Temperatures

The Lows also started well below average, and ended around the average.


The average Low of -0.9°C was also a bit on the cool side, but still above years like 2012 at -2.1°C  and 2002 at -2.7°C.

We had 21 Lows below freezing, which is a lot. In terms of recent years that ties 2009 for the most. We only had 1 Low below -5°C though, compared to 2012 and 2004 which both had 10. And we didn't have any October Lows below -10°C.


October Overall

When we combine the Highs and Lows, the mean temperature this October was 4.6°C. That's below the 20th century average of 5.3°C, and ranks 2018 as 92nd-warmest October out of 138. This chart also shows the Highs & Lows separately, and they both ranked in the low 80s.

One thing that is interesting in this chart is that the average Low temperatures for October have increased over the last century - from about -2°C to +1°C. But the average Highs have actually dropped a bit - from 12°C to 10°C. We didn't see that in September, and it's not very common in other months either. That will probably be the subject of a future post.


Warm & Cold Months

For this year so far then, October ranks as the 5th month that was below the 20th Century average - along with February, March, April and September. January and May-August were all warmer than the 20th Century average.


The Horserace

The end of October is really the point where we transition into real-winter (instead of fake-September-winter). So now is a good time to see how 2018 compares over all.

When we sum up all of the temperatures for the year, right now 2018 is sitting just a bit above the 20th century average. That puts in at the lower end of recent years, along with 2009, 2014 and 2013, and ranked somewhere around 50th~70th overall. Following the red line, we can see the sharp dip we took during the September coldsnap.


Precipitation

After our very precipitation-y September, October was right around average at 20mm. And Blatchford was just a bit below the International, at 16mm. Last year we had just a bit more, with 25mm.


Snow

And after our extremely, record-breakingly snowy September, October's 8cm was right on the average. Last October we had almost twice as much, at 15cm.



Even though we didn't get a whole lot of snow in October, the International did record 6 days with snow. That's down from 8 in September, but above the 4 last year, and the average of 3.


Snowdepth

At the cold start of the month we had snow on the ground for about a week - shown here in the orangey/gold. But once things warmed up, it disappeared.

October isn't typically the month when we get lasting snow though. But the first few weeks of November is when it usually shows up, as we make the jump into winter.


November Temperatures


...and speaking of winter, here is the recent temperature history for November.

The good news is that there are frequently still a lot of days above freezing - recently 2006 had 7 and 2017 had 9, but plenty of years were up around 20. The less good news is that about half of the time November is when we'll see our first -20°C of the winter.

2018/10/28

Halloween 2018

Today we're taking a look back at Edmonton's history of Halloween weather.

Temperatures

For the last 30 years the average High on Halloween has been 4.5°C, and the average Low -3.7°C.

Last year in 2017 the High was a little below average at 3.8°C. But 2013-2016 were all above average with 2016 at 5.1°C, 2015 at 9.7°C, 2014 at 5°C and 2013 at 10.7°C.

The last time that we had a below-freezing High on Halloween was 2012 at -6.6°C, and with a Low of -9.1°C

For some trivia:

  • Edmonton's warmest Halloween was 1981, which was way up at 19.9°C
  • Edmonton's coldest Halloween was 3 years later in 1984, with a high of -18°C and a low of -24°C. 1984's High temperature of -18°C was lower than the Low temperatures of every other Halloween except for 1991.
  • Since 1981 Edmonton hasn't recorded a Halloween above 15°C. But prior to that there had been 9 warm Halloweens.
  • Prior to 1984 Edmonton hadn't recorded a Halloween below -15°C. But since then we've had 3 in 1984, 1991 and 2004.


Recent Rain & Snow

Last year's Halloween of 2017 wasn't particularly cold, but it was really wet: the International Airport recorded 3.6mm of Rain and 5.2cm of Snow.

Prior to that we'd gone more than a decade without snow on Halloween, with 2006 recording just a skiff of snow at 0.2cm.

The snowiest recent Halloween at the International was 1999, with 10.2cm of snow. At Blatchford that year only 2.2cm of snow was recorded, and it's snowiest recent Halloween was 1994 with 3cm (although Blatchford's records stop after 2007).


Historic Rain & Snow

Going further back into history, Blatchford's snowiest recorded Halloween matched the International's 10.2cm, but Blatchford set its record in 1882 while the International's was in 1999.

2017 actually ranked as the International's 2nd-snowiest Halloween with its 5.2cm, and also as the International's 2nd-rainest Halloween with its 3.6mm.


Snow-on-the-Ground

On October 31st the International usually does not have any snow on the ground. Recently 2017 had 2cm, and 2013 had 1cm.

But going back a bit further, 2001-2006 were really stand-out years for snow on the ground. 5 of those 6 years had 2cm-or-more of snow on the ground at Halloween.



On October 31st we usually don't have any snow on the ground, but over the next month that will change. November is when we typically start to get lasting snow, and on October 31st the average snowdepth is pretty close to 0cm, but by November 30th that average will increase to 10-15cm.

In this chart only 13 of the 56 years since 1961 had more than a dusting of snow on the ground on Halloween. But by the end of November that number flips to only 11-of-56 years without snow.

2018/10/18

Record Watch: October 17, 2018

So we set a new record today, and for the first time in a while it was for a really warm day instead of a really cold one.


On October 17th we set a new record High temperature of 24.7°C.

That was our warmest day since September 6th at 26.1°C, and also our only 20°C day since September 6th. And if we go a little further back, since August 22nd the only 2 days to hit 24°C were September 7th and October 17th.

On August 9th we'd also set a record for warmest-High, at 34.5°C. But then more recently we'd set records for coldest-Highs, on August 12th at 11.6°C and September 13th at 1.3°C.


October 17th History

The previous High temperature record for October 17th had been 22.8°C, set in both 1901 and 1903.

The last time that we had an October 17th which hit 20°C was way back in 1963m at 22.2°C. Although last year was pretty warm, with October 17th 2007 hitting 19.8°C.


The Week of October 14th Through 20th

This chart shows the 50 warmest temperatures for the week of October 14-20.

October 17th is just one day, and when we look at the rest of this week most of the days have higher records. The coolest record for this week is the 19th, down at 22.8°C. But the record for October 14th is way up at 28.3°C, set in 1945.

Looking at the breakdown of this Top-50 by decade, the 2010's only have 2 days, the 2000's had 0 days, and the 1990's and 1980's each only had one. In comparison, if we go further back the 1920's and 1960's each had 8 days in the Top-50, and the 1960's were the leader with 9 days.


Late October Warm Days

So this was a pretty warm day for mid-late October.

In the last 20 years there have only been 5 other days over 20°C this late in October:

  • 22°C on Oct 20 2014
  • 25°C on Oct 24 2007
  • and in 1999, 21°C on Oct 19, 22°C on Oct 22, and 21°C on Oct 23

How Often Do We Set Records?

Today's record feels likes it's worth celebrating because we had such an unrelentingly cold September and early October. But setting a new High temperature record is not particularly uncommon.

On average we set about 4 new records each year. So far in 2018 we've only set two, with August 9th at 34.5°C and now October 17. In 2017 we set 4, in 2016 we set 6, and in 2015 we set 5.

Last year we looked at this in detail in How Often Does Edmonton Break Temperature Records?

2018/10/08

Thanksgiving 2018

Today we'll be looking at the weather for Thanksgiving 2018.

The short version: pretty cold but not really cold; pretty snowy but not really snowy.


Temperatures

This chart shows the temperatures for the Thanksgiving weekends (Friday-Monday) going back to 1995.

Thanksgiving 2018 was on October 5-8, which as early as it can possibly be. Other early Thanksgivings here were 2001 and 2012. But even a late Thanksgiving can only be as late as October 11-14, and recently we had those in 1996, 2002 and 2013.

The warmest recent Thanksgiving was 2010 with the Friday, Saturday and Sunday all above 25°C. And the hottest single Thanksgiving weekend day here was the Saturday of 2015's Thanksgiving weekend, at 26°C.

The coldest recent Thanksgiving was 2009, with all 4 Highs below freezing. 2016 was also pretty cool, with all for Highs below 5°C.

How does 2018 compare?

The average High around Thanksgiving is 11.5°C, and on Friday and Saturday we were just below that at 10.2°C and 11.2°C respectively. Then Sunday was cool at 7.4°C. As I'm writing this it looks like Monday's High will be about -1.8°C, and that's very cold. Since 1995 the only other Thanksgiving with any Highs below freezing was 2009.

The average Low for Thanksgiving is 1°C, and this year all of the Lows were a few degrees cooler down around -2°C and -3°C. 2016, 2009, 2008, 2000, & 1997 all had Lows which dropped below -5°C.

So Thanksgiving 2018 was pretty cold but not really cold.


Rain & Snow

This chart shows the Rain and Snow recorded at the International Airport since 1995.

This year Sunday had 2.2cm of snow & 0.4mm of rain, and Monday had 2.0cm more of snow.

For some recent comparisons:
  • 2017 had 0.2mm of rain on the Saturday, and 0.4cm of snow on the Sunday.
  • 2016 was a big snow year, with snow on all 4 days for a total of 12.5cm.
  • 2015 had a total of 1.4mm or rain on the Sunday and Monday.

Before that we need to go back to 2009 to find a Thanksgiving with some Precipitation, and it had 1cm of snow across 3 days.

The really notable Thanksgiving here was 1998, with 2.6mm of rain and 16.2cm of snow.

So Thanksgiving 2018 was pretty snowy but not really snowy.


Our Cold, Cold, Cold September Continues...

Last week we talked about the historically cold September of 2018, and while temperatures have moderated a bit since then, we've still been below average - in some cases (like Thanksgiving Monday) a lot below average.


Winter 2018-2019 Snow Totals So Far...

This chart shows our cumulative snow totals for the winter of 2018-2019, so far. And thanks to the historically snowy September 2018 we're well above any recent years, with a total of 43.2cm. The average doesn't hit 43.2cm until later December.


Lasting Snow


This chart shows the depth of snow-on-the-ground at the International Airport. 2018-2019 isn't included yet because so far in October there hasn't been much going on.

At Edmonton Weather Nerdery we don't make predictions. But typically we don't get lasting snow until the last week of October at the earliest.

2018/10/01

September Review / October Preview

It's time to pull off the band-aid to take a look back at a very, very, very cold September.

Edmonton is obviously not known as a warm city, and it is certainly true that sometimes autumn can show up very early. But today we're going to see that September 2018 was not just a normal, cold September. September 2018 was especially unseasonable, and it was something that Edmonton hadn't seen in 50 or 100 years, if ever. Last week we looked at Edmonton's History of cold Septembers if you are interested in a bit more background.


September High Temperatures

We're at the point in the year where our temperatures are falling rapidly. At the beginning of September the average High temperature is about 20°C, and by the end of September it drops to 14°C. At the end of October it will be down to 5°C, and then -2.5°C by the end of November.

But when we look at the High temperatures for September 2018, the "average" had very little to do with anything. For the whole month there were only 3 days - the 5th, 6th, & 7th - which were above the average, and those are highlighted in red.

The other 27 days were all below average, and are highlighted in blue. We had 8 daytime Highs that were 10°C or more below average. And with all of those really cold days we set one all-time record for coldest High, on September 13th at 1°C. And we also set 6 other coldest-since-1996 Highs.

On this chart it's worth noticing how many of our September Highs weren't just below average for September, but also fall below the averages for October too.



When we look at the numbers, September 2018 is like nothing in recent memory. Our average High was way down at 11.1°C, compared to 18.8°C last year or 20.7°C in 2013. The 2nd coldest September in the last 20 years had been 2004, and it was way up at 14.7°C.

This September only had 3 days which hit 20°C, while last year we had 15, and the average is 10. We also had 15 days with Highs of 10°C or less, while the 2nd-coldest year here was 2006 with 6 days, and the average is only 2 days. And we had 7 days of 5°C or less, with the 2nd-coldest recent years at 2 days, and the average at only 0.4 days.


October High Temperatures

Normally we leave next month's temperatures until the very end of these month-in-review posts, but this time it's worth taking an early look at October.

Our September average High of 11.1°C was just a little bit below last October's average of 11.2°C. And in the last 20 years a warm October has had average Highs around 13°C or 14°C, while a cold October is down around 5°C or 6°C. So September 2018's Highs would fit right in as a slightly warm October. Not even a really warm October - just a slightly warm one.

September's 3 days at 20°C, 21 days below 15°C, and 5 days below 5°C also wouldn't be out of place in a warm~ish October.


September Low Temperatures

When we switch over to Low temperatures it's a similar story. There were a total of 4 days with Lows above the average - the 6th, 7th, 8th, & 26th. We didn't set any records for all-time Lows, but 8 nights hit coldest-since-1996 temperatures.



Looking at the numbers, we had 8 nights below freezing. In the last 20 years we've averaged only 1 frost in September, and the 2nd-most frosts was 2003 with 5. The last time that we had 8 frosts in September was 1985 which also had 8, and before that 1972 had 10. The September with the most recorded frosts was 1926, with 15.

In the past 20 years the average Low has ranged from a warm year like 2009 at 8.7°C down to a cold one like 2010 at 4.7°C. And this year our average was almost 2°C colder than a cold year, down at 2.8°C.


October Low Temperatures

Looking at October Lows, in recent years the monthly average Low has ranged from -2.7°C in 2002 to +2.5°C in 2010. And so this September's very cold average Low of 2.8°C would be a little bit warm for October.

In October the average number of frosts is 13. This September we had 8, which is a lot for September, but would be on the low side for October. Recently the Octobers of 2015, 2014, 2010, 2007, & 2003 were all similar to September 2018 with 7-9 frosts. This September we didn't have any nights which hit -5°C, but in October its typical to have a few of those.


September Ranking

So we've seen that September 2018 was a lot like an October, and that it was much colder than other recent Septembers. But how does it compare to history? In this chart we have the average September temperatures going back to 1880.

The orange & blue bars in the chart are for the Mean daily temperature (the average of the Highs & Lows), and at 6.917°C this was the 5th coldest September ever recorded. And it was essentially in a tie with 4th-place 1972, which was at 6.913°C. The colder years were 1934 at 6.8°C in 3rd, 1965 at 6.3°C in 2nd, and the very-chilly 1926 at 5.4°C as Edmonton's coldest September. The only other recent" September in the bottom-10 was 1985 in 9th place at 7.9°C.

During the 20th century the average-Mean temperature for September was 10.8°C, and so this year we were 4°C below that. And over the years September's average has risen, and recently it's been up around 13°C, so 2018 was 6°C colder than that.

In this chart the High & Low temperatures are also shown as orange & blue lines:
  • 2018's average-High of 11.1°C was the 2nd coldest recorded, falling behind 1926's 10.3°C, but just ahead of 1934's 11.6°C. 
  • 2018's average Low of 2.8°C is about 27th coldest, because Lows have trended upwards quite a bit over the years. The last time that we had an average Low this cold was 1972, at 2.3°C.

One final bit of trivia is that 2018's average-High of 11.1°C is actually below the average-Mean that we've seen in recent years, which had been up around 13°C.


2018 so far...

Looking back over 2018, we had a really late spring with a very cold April. But then at the beginning of the summer we had a really warm May with July-like temperatures (and I hoped that everyone was able to take advantage of it). And now we've had an unfortunately early end to the summer with an October-like September.



And this is what that looked like on a day-to-day basis.

In April we had a number of days down at the very bottom of the range. But then in May temperatures jumped to the very top of the range, and they stayed there through June. July was pretty normal, and then in August the smoke rolled in. And the summer of 2018 came to an abrupt end in our bottom-of-the-barrel September.


Precipitation

We're going to start by talking about Precipitation in general (rain & snow-equivalent), and we'll switch to just talking about snow later on.

This chart shows the total number of days with recorded Precipitation at the International and at Blatchford. And as gloomy as things were in town, Blatchford only record precipitation on 13 days, while at the International it was 18 days. This chart goes back to 1995 as a reference, and in those years the previous highest was 1996 at 16 days. The International's the records go back to 1961, and
2018's 18 days also sets a new overall record beating 1964 and 1978 which both recorded 17 days.


Total Precipitation

In terms of total Precipitation for the month, the International recorded 79mm, while Blatchford was down at 58mm.

The International's 79mm was right up at the top of the recent range for September, coming in just below 80.4mm in 2006. But going back a bit further, in 1984 the International recorded 116.3mm and in 1978 it recorded 141.5mm. So 2018 was a lot, but was still well down from the records.

The International's 79mm also made September the month with the most precipitation so far this year, beating out June's 76mm.


2018 Cumulative Precipitation

And with all of that precipitation in September that brings the International's total for the year to 387.7mm, which is just above average for this time of year. Blatchford has only recorded about three-quarters of that, with a total of 302.1mm.


Snow

It's time to talk about September snow.

You might think "Edmonton is cold and always gets snow in September" but in this chart each of the bubbles represents and early snowfall, and September has usually been pretty empty. We looked at this in more detail in First Frost & First Snow.

But September 2018 is definitely pretty crowded compared to most years (2017 was too), so lets take a closer look.


Snowy Days


The International recorded 8 days with snow this September. That's a lot. Going all the way back to 1961 the previous highest year was 1985 with 5 days of snow. And since 1995 the average had been less than 1 day. For recent years 2017 had been the previous leader with its 3 snow days, but 2018 has changed all that. 8 snow days is right at the average for our real-winter months like November-March.


Total Snow

In terms of total snow, this September the International recorded 38cm. That's a lot. It's more than we got in any of the months last winter. And it's basically twice the average amount for any of the real-winter months: in November the average snowfall is 19cm, in January it's 21cm, in March it's 20cm, etc.


A New Snow Record

And so, 38cm at the International doesn't just set a new record - it blows away the competition. The previous snowiest September at the International was 1965, with 12.9cm. And this September we had 38cm. And that's a bit ridiculous.

This chart switches between total Precipitation, Rain & Snow for September. In 2018 Rain & Snow were fairly evenly split, with 40.6mm of rain and 38.4cm of snow. Typically though, September is much more of a rain-month than a snow-month.



Going even further back into the records, the snowiest September ever recorded at Blatchford was 1926 with 28.5cm. Environment Canada doesn't track snowfall at Blatchford anymore, but the International's 38cm is well ahead of any of the years here.

And here we see that even going back a century or more September has not usually been a particularly snow month in Edmonton.


Summary

Today we had a lot to talk about, because there was a lot going on this September:
  • 2nd-coldest High temperatures and 5th-coldest Mean daily temperatures.
  • More snowy days than we've ever seen in September, more snow than we've ever seen in September, and even more snow than we see in most winter months.
So on the one hand, we might never see another September like this. But on the other hand, the September that we just had was basically a fake-October, and we're about to enter real-October. So we can probably expect another month of what we just had.

If all of that is getting you down, last week we looked at the history of Edmonton's Cold Septembers, and asked: "Does a cold September mean a cold winter?" And the answer was "No". After this historically cold September, the chances that we'll have a warm winter are still about as good as a coin toss.