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.

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.

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?

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.

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.