2019/02/20

Deepfreeze 2019!

The great deepfreeze of 2019 ended on February 18th. Things were still cold after that, but that was the end of the official streak, so let's see how it compared to the deepfreezes of the past century.

Today is a bit of a long-gap sequel to two posts from a few years ago:
In those posts we looked at recent deepfreezes, and also at Edmonton's very longest deepfreezes. Today we will be covering some of that again, but this time we have a few new charts to play with which should show how often these occur.


The Lows

The winter of 2018-2019 had been fairly mild...but then February happened. And February wasn't just "typically" cold - the first 18 days were right at the very bottom of the range of temperatures that we've seen in recent years, including 10 days with coldest-since-1996 temperatures. That was still typically about 10°C warmer than the coldest-since-1880 records, though.



In those first 18 days we had 3 days which hit -30°C, while in the past 20 years we had only had 2 other -30°C February days (in 2018 and 2008).

We had 14 Lows which hit -25°C, compared to the coldest recent February in 2014 which only had 6.

And we had 18 Lows hit -20°C, when recent cold February's had topped-out at 12 in 2018, 13 in 2014, and 15 in 2011.


Recent Coldsnaps

For recent winters going back to 2010-2011 the longest stretch of -25°C Lows that we had had was 5, and that was last winter. This year we went 9 days straight, took one day off, and then had another 4 day stretch.

For Lows of -20°C both 2010-2011 & 2017-2018 had stretches of 9 in-a-row. This winter we doubled that with 18 Lows of -20°C or colder in-a-row.

So we haven't seen anything like this is "recent" memory.

At the end of January this winter had been mostly deepfreeze-free. But February fit an entire winter's worth of -20°C and -25°C days into just a few weeks.


Lows of -25°C or Below: 9 in-a-row

The stretch of Lows of -25°C or colder ended on February 10th, after 9 days in-a-row. That was not the end of the -25°C Lows, which only took one day off and then returned for another 4 day stretch.

9 in-a-row is Edmonton's 39th longest stretch of -25°C Lows since 1880, and the longest since 12 days in January & February 1996. And before that we need to go back to 14 days in 1984.

Edmonton's longest recorded stretch of -25°C Lows was the infamous January of 1969, with 26 in-a-row.


Lows of -20°C or Below: 18 in-a-row

For Lows of -20°C or below we went 18 in-a-row, which made it Blatchford's 22th longest streak.

The last time that we had a streak this long was back in the mid-1990s, with 23 Lows of -20°C in-a-row in 1996, and also 17 days in 1993. In the last 20 years we had had one 10 day streak in 2003, and everything else had ended at 9 days. So this was twice as long as the longest coldsnaps that we have seen recently.

Edmonton's longest recorded stretch of -20°C Lows was 46 (46!) spanning from December 1949 into January 1950.


This chart shows how the number of long deepfreezes has changed over time.

To make this make sense there's a bit of cheating going on: on the various slides of this chart a 15-day deepfreeze is counted as 3 x 5-day deepfreezes, 2 x 6-day deepfreezes, 2 x 7-day deepfreezes, 1 x 8-day, and etc. Without that it would be counting the really, really long deepfreezes as 1, and that isn't fair.

One thing to notice from this chart is how much more rare 10+ days deepfreezes have been since the mid-1990s. From 1980-1996 there were 10 10-day streaks, and since there there have only been 2 in 2019 and 2003.


Calgary

Calgary also had its own generational deepfreeze, with 14 -20°C Lows in a row. That made it Calgary's 27th longest streak, and the longest since 18 days in 1996. Calgary's record is 31 days from 1965.


The International Airport

In the past we have talked about how much colder the Edmonton International gets than Blatchford, most notably in The Edmonton International Airport: Part 2. Typically during the winter the airport's Lows will average about 3°C below Blatchford, but on really cold days it gets a lot colder. And that happened again during this deepfreeze.

Blatchford had 3 -30°C Lows, while the International had 10. And those 10 days included 5 which were -35°C or colder with one -41.2°C on February 5th.

During this deepfreeze the biggest gap between Blatchford and the International was 10°C on February 4th, with Blatchford at -29.5°C while the International was down at -39.5°C. And there were 10 days where the International's Low was at least 5°C colder than Blatchford.


The Highs

The High temperatures weren't quite as exciting as the Lows, but we set 9 coldest-since-1996 Highs.


Highs of -15°C or Below: 11 in a row

On February 13th we hit a balmy High of 14.3°C, which ended our run of Highs of -15°C or below at 11 days. That was the 31st longest streak since 1880, and the longest since a 15 day streak in 1998. And before that we need to go back to 1982 for a 17 day streak.

Edmonton's longest run of Highs of -15°C or below was 28 days in January 1934.


Highs of -10°C or Below: 18 in a row

And one more streak: we had 18 days in-a-row with Highs of -10°C or below. 18 days at -10°C doesn't seem all that impressive, but it was actually Edmonton's 15th longest stretch.

This was the longest since 23 days in 1996, and Edmonton's longest recorded stretch of -10°C Highs was January 1950 again.

So that about covers the actual deepfreeze days, but the rest of February 2019 was pretty cold too. We will look at that in the February review at the end of the month.

2019/02/19

Months Below Freezing

Today we are going to look at some winter trivia.

Environment Canada's temperature data for Edmonton goes back to July, 1880. That is 139 years, and about 1,660 months.

How many of those months recorded no days with a High temperature above freezing?

Any guesses?


It turns out that since 1880 Edmonton has recorded 14 months where the High temperature never reached above 0°C.

The most recent was December 2010, and before that February 1979.

Broken down by decade the numbers are:
  • 1900s: 2
  • 1910s: 1
  • 1930s: 1
  • 1950s: 4
  • 1960s: 2
  • 1970s: 3
  • 2010s: 1
  • 1880s, 1890s, 1920s, 1940s, 1980s, 1990s: none
Over the years there are a few instances where data is missing - a few whole months are gone in the 1880s, and also in 1993 for some reason. Any months with missing data are not included in this count. So potentially these numbers might be a tiny bit higher, but only by about 1 or 2 months at most.


Edmonton International

This chart adds the International Airport in as well, where the data only goes back to 1961.

Since 1961 the International has had 9 months without a High above freezing. Those have matched the freezing months at Blatchford, but also added the Decembers in 1995, 2009 & 2012.

Now let's check on some of our neighbours.


Calgary

Since the 1880s Calgary has only had 1 month with no Highs above freezing: January 1950. That month is also on Edmonton's list.


Regina

Regina is quite a bit busier, with 48 months since the 1880s.


Winnipeg

For Winnipeg there have been 119 months with no Highs above freezing. On this chart there isn't enough room to include labels for everything.


Montreal

And finally, Montreal has had 5 months without any Highs above freezing. The most recent one was February 2015, and the earliest was February 1901.


Comparisons

This chart cycles through the various cities.

In Edmonton, Calgary, and Montreal it is quite rare to have a month without a High above freezing. In Regina it happens on-average about every 3 years, and in Winnipeg it's almost yearly.



The most typical month without any Highs above freezing is January, which isn't a surprise. Although the range is 1 for Calgary, 2 for Montreal, 6 for Edmonton, 22 for Regina, and 57 for Winnipeg.

Of these cities Edmonton is the only one to have had a completely freezing November, back in 1973.

So that's it for the trivia.

The reason that we bring this up right now is that with about a week left in February 2019 it looks like there is a good chance that it will be added to this list for Edmonton (and also possibly for Calgary).

2019/02/16

Family Day - 2019 Edition

Today we are looking at the history of weather for the Family Day long weekend.

Temperatures

Family Day was introduced in Alberta in 1990, and a holiday in mid-February in Alberta maybe doesn't seem like such a great idea? But generally the temperatures have been fairly warm, with an average High of -2.2°C and an average Low of -11.3°C.

2018 was fairly cold, with Highs around -10°C and the Lows closer to -20°C. And 2019 will probably be a bit colder than that. But the 5 Family Days from 2012-2017 all had Highs around or above freezing.

2016 was the warmest-overall Family Day weekend with all three days between 5-7°C. The coldest-overall was back in 1994, and it is the only Family Day weekend that was a complete deepfreeze, with all three Highs down around the -20°C mark. For the very first Family Day in 1990 the temperature swung from a low of -31.2°C on the Saturday up to a balmy high of 2.6°C for the holiday Monday.


Precipitation 

For precipitation it is no surprise that snow happens a lot more often on the Family Day long weekend than rain does. But the day here with the most precipitation was February 14, 2015 (the Saturday of that long weekend) with 7.4mm of rain.

In 2018 there was no precipitation, and 2017 had a mix of rain and snow.


Snow on the Ground

And finally, this chart shows how the snowdepth at the International Airport changes from February 14-21, which is the week in which Family Day moves around.

The average is about 20cm, and this year we are high at 33cm. Last year was also a bit high at 25cm. And during the really warm week in 2017 the snowdepth fell from about 12cm down to 2cm.


Updated for 2019:

Family Day Weekend 2019: the coldest since 2011, and much colder than 2012-2017.

2019/02/13

Valentine's Day 2019

Today we are taking a break from all of the talk of deepfreezes to take a quick look at the history of Valentine's Day weather in Edmonton.


Temperatures

In recent years our average high on February 14th has been -3°C, and the average low -11°C.

Last year's Low was pretty chilly at -18.1°C, but the High was up at 2.8°C. And 2017 was almost record-breaking, with a High of 10.3°C and a Low of -1.4°C.

Right now the record temperatures for Valentine's Day were all set a long time ago. The warmest High was 10.6°C back in 1907, and the warmest Low was 2.8°C in 1913. The coldest High was -40.6°C in 1904, and the coldest High was -30°C in 1936.

This Valentine's Day will probably not be warm. We haven't had a super-cold Valentine's Day in a long time though - 2007 was chilly with a low of -22.4°C, but a reasonably nice high of -7.4°C. For a true deepfreeze you have to go all the way back to 1979 with a high of -24.1°C and a low of -35.1°C.


Precipitation

In recent years the most notable Valentine's Day precipitation was 2015 with 7.4mm of Rain.

Typically though, Valentine's Day precipitation comes in the form of snow. Blatchford's snowiest Valentine's Day was 1921 with 19.1cm of snow, but in recent decades the snowiest days have been around 2cm.


Snow on the Ground

The average snowdepth at the Airport for this time of year is about 20cm. Last year it was a little high at 25cm, and in 2017 & 2018 it was a little low at around 12cm. This year we are on the high side again at 33cm.


Updated for 2019

If you had guessed that this was going to be a cold Valentine's Day, you were right! It was the coldest one since 1979. And in 2019 there wasn't any precipitation.

2019/02/01

January 2019 Review / February 2019 Preview

It's time for the January 2019 month-in-review. Was this January warm, or cold, or not too warm or not too cold? Let's find out.


High Temperatures

Here we have the High temperatures for January, compared to the range of Highs since 1996.

January 2019 set one warmest-High-since-1880 record on January 2nd at 8.6°C, and had two more warmest-since-1996 days on January 26th & 27th.

For most of the month the Highs were above average, although there were a few cooler days around the middle of the month.


Looking at the numbers, the average High was -1.9°C. That's quite warm, but is below recent years like 2014 at -1.8°C, 2006 at -0.4°C, or 2001 at 1.7°C.

We had 4 Highs of 5°C or more, which is average for January. We also had 14 Highs of 0°C, compared to an average of 12. On the cold side of things we only had 1 High of -15°C or colder, while the average is 5.


Low Temperatures

Like the High temperatures, the Lows spent most of the month above the average. January 2nd also set a warmest-Low-since-1880 record at 1.2°C, and the Low of 2.7°C on January 26th was the warmest-since-1996.


In January 2019 we had 2 Lows above freezing. That is not unheard of, but it is pretty rare. In the last 20 years 2015 had 3 Lows above freezing, 2014 had 3, 2013 had 1, and 2002 had 1, and that was it.

This January we had 4 Lows of -20°C or colder, while the average is 8. We also didn't have any Lows of -25°C, and in the last 20 years that had only happened in 2006 and 2001. So it was a mostly deepfreeze-free month.


Coldsnaps

The forecast for next week is calling for some very cold days, but as-of January 31st this has been a pretty mild winter so far. We have had 5 Lows hit -20°C, and none hit -25°C. So far that is fewer than any winters going back to 2010...although we will wait until the end of March to see how this winter really scores.


Warm & Cold January's

When we add up the High & Low temperatures, January 2019 was the 16th warmest since 1880. During the 20th century the average mean daily temperature for January was -13.5°C, and this year we were up at -6.7°C.

January's records are kindof amazing:
  • Edmonton's coldest January in 1950 had a mean temperature of -27.8°C. The average Low for January 1950 was -32.4°C, compared to -11.5°C this year.
  • Edmonton's warmest January in 2001 had a mean temperature of -2.7°C, and an average High of 1.7°C.

The gap between those records is huge.


Looking back at the past few months, our quite-warm January follows a pretty-warm December and November. And lets agree not to talk about October or September.


Over the past 20 years most of our January's have been warmer than the 20th century average - they appear as the row of orange bubbles at the bottom of this chart. The only recent January which was colder than the 20th century average was 2004.

February's have also generally been warmer than the 20th century average - the exceptions being 2001, 2007, 2011, 2014, & 2018. Since last February was quite cold maybe we will be lucky this year.

We looked at the way some months have warmed more than others in The Months through the Years.


Snow

For snowfall at the International January had 15cm, compared to an average of about 21cm. That was down from the 31cm that we had in December, but it was a perfect match for the 15cm in December 2018.


Snowdepth

The warm temperatures of the last few days have dropped the snowdepth at the International down to 16cm.

The average for this time of year is around 20cm, although as I type this there is a snowfall warning in effect, so things are likely going to change rapidly. The end of January was when things changed last winter too, with the snowdepth jumping from 8cm to 34cm over the course of a week.


January Rain

We also had some rain this month on the 25th and 27th. January rain always seems to surprise people, even though it's not particularly uncommon.


With a total of 0.9mm this was not a particularly rainy January. Recently 2014-2016 all had around 3~4mm, and 2005 was the International's 2nd-rainiest January with 9.5mm.


February Temperatures

For February temperatures, they are usually a lot like January with 10-15 Highs above 0, and 5 Lows below -20°C. Since 2000 there have only been two -30°C in February - one was last year on February 4th, and the other was February 9th, 2008. February is also on-average the least-snowy of the main winter months.