2019-2020 Winter-in-Review - Temperatures

Today we are going to look back at the winter of 2019-2020 to put it in context. We have been doing this for a few winters, now:

• 2015-2016 Winter in Review
• 2016-2017 Winter in Review - Temperatures
• 2017-2018 Winter in Review - Temperatures
• 2018-2019 Winter in Review - Temperatures

Normally at Edmonton Weather Nerdery when we talk about "winter" we use November 1st through March 31st, because the temperatures make a nice mirror:

The average Highs at the beginning of November are about 5°C, and by the end of March they are back up to about 6°C. And the average Lows are about -3°C at both the beginning of November and end of March.

The problem with the winter of 2019-2020 is that it seems like it's never going to end. The last two weeks of March were cold, and that has carried on into the first two weeks of April. And we even hit -20°C in April for the first time since 1982.

So for the winter of 2019-2020 we will include early April as well.

Low Temperatures

Here we have the Low temperatures for the winter:

• The cold started early, with a few days near -20°C at the beginning of November, but after that things were fairly mild through New Year's.
• Then we had the two-week mid-January deepfreeze, and on January 15th temperatures dropped all the way to -37.6°C (or -42.3°C at the International). That was Blatchford's coldest day since January 19th, 1996 which hit -37.8°C, and before that January 25th & 26th 1972 hit -38.9°C and -41.1°C respectively. It was very unusual.
• February had a short deepfreeze in the middle of the month, hitting -26.9°C, but also had quite a few above average days.
• Then March was pretty cold and spent some time near the bottom of its recent range.
• And April started very cold, with some new coldest-in-30-year Lows.

The bargraph at the bottom of this chart compares all of the Lows for each winter, and if you click or hover on 2019-2020 its Lows ranked as #55, with an average Low of -11.8°C which was just a bit below the 30-year average. You can click on any of the other bars to see the temperatures for a warm winter like 2015-2016 of 1930-1931, or for a cold winter like 1886-1887.

You can also change this from Lows to Highs, which ranked as #53 warmest. And you can change the date range to exclude the cold end of March and early April: just for November 1 through March 15 this winter had the #36 warmest Lows and #33 warmest Highs, so the past few weeks really dragged it down.

We will look at a lot of charts today, which all say basically the same thing - this was a fairly typical winter, with a cool spring. So if you find a chart that you like trying clicking around or changing the sliders to explore the data a bit.


2019-2020 Compared to the 20th Century Average

We often use the average temperatures for the 20th century as a handy benchmark, and here we the temperatures for each day of the winter compared to their 20th average. The red lines show the Means (High & Low), the Highs, and the Lows, and a warm day moves the lines up while a cold day moves them down.

For all 3 lines we see a slight dip at the beginning November for the cool start to winter, and then after that the warm temperatures pushed the line upwards until mid-January. Then in mid-January we had the deepfreeze which pushed the line down. Then the line climbed again until early-March, and our late, cold spring pushed it down again.

This isn't my favourite chart, but the mess of spaghetti lines in the background represents each of the winters going back to 1880. And so while 2019-2020 was not particularly warm, but on average it was about 1°C warmer than the 20th century average. We can also see that at the beginning of March this winter ranked as about the #30 spot, but fell to #56 with the cold spring.


Warm & Cold Months

Here each month of the year is represented by a bubble. Months which were warmer than the 20th century average are orange, and colder months are blue. And the size of the bubble represents how much warmer of colder they were.

November, December, January & February are all orange bubbles ranging from 1.1°C above average for November & January, to 3°C for December, to 4.3°C for February. March was the only below-average month, at -1.6°C.

It is important to make the distinction between the 20th century average and recent years, though. January 2020 was warmer than the 20th century average, but it is the smallest bubble here since 2004, because recently we had had a string of very warm January's. February 2020 was much warmer than the giant blue bubble for the incredibly cold February 2019. And the bubbles for November & December 2019 are a pretty close match to November & December 2018.


Across Canada

And here we have a quick comparison of the winter across Canada:

• Winnipeg through Montréal all had a relatively cold November.
• All of the cities were above average for December, January & February.
• Edmonton's cold March was shared by Vancouver, Calgary & St. John's. While Regina through Montréal were all from 2°C to 4°C above warmer than their averages.

Radial Chart

This chart is really just for show, but it combines a bunch of interesting information in one place:

• The big circle at the top shows how relatively warm or cold each winter. 2019-2020 was pretty similar to 2018-2019. And those were both a lot warmer than 2017-2018, but a lot colder than 2015-2016. And we also used to get a lot more blue lines a century ago than we do today.
• The smallest circle on the lower left is each month, with the cold March in blue and the warm February in orange. If you click on any of those months
• The small~ish circle lower down in the middle is how much above or below average each day of the winter was. For the January deepfreeze there is a blue spike for January 15th which was 18°C below average. And there is another blue spike at the beginning of April which was 15°C below average.
• The small~ish circle on the lower right is the actual, daily temperature. And so even days which where well above average (like January 1st, or February 1st) still had mean temperatures below freezing.

This is another fun chart to play around with by changing the date range, switching between Highs/Lows/Means, or looking at the results from other cities. Montréal had a warm winter (#17 spot) while St. John's was fairly cool (#65 spot)


Really Cold Days

This chart shows the number of Lows which hit -20°C each winter. The winter of 2019-2020 had 18 of those, which was less than the previous 3 winters, but more than 2015-2016 which was down at 6. Right now we average about 23~ish per winter, which is about half as many as a century ago.

The winter of 2019-2020's first -20°C was a -24.2°C  on January 9th, which is very late. But then the final -20°C of the winter was a -20.8°C on April 2nd, which was the first -20°C in April since 1982.

The winter of 2019-2020 has 9 Lows hit -25°C, which is about average, although there is a lot of variation between individual winters. 2015-2016 only had 1, 2016-2017 had 6, 2017-2018 had 11, and 2018-2019 had 19 (mostly during the incredibly cold February).

The winter of 2019-2020 has 4 Lows hit -30°C, all during the January deepfreeze. 2018-2019 also had 4, 2017-2018 had 3, and before that 2015-2016 & 2016-2017 both had none.

And finally, The winter of 2019-2020 actually had a Low below -35°C, with January 15th down at -37.6°C.

A -35°C is not something that happens every year at Blatchford. That last one was more than 10 years earlier on December 13, 2009 at -36.7°C. There was also one in 2008, 2004, 1997, 1995, etc.

This chart shows how big the gaps are between -35°C Lows at Blatchford. The 3,863 from December 13, 2009 to January 15th, 2020 had been the longest recorded.


Warm Days

We have talked about how 2019-2020 was a cool~ish winter, but from November 1 to April 7 (158 days) 76 had Highs of 0°C or more. That's 48% which is right on the average.

If you switch the date range in this chart to just the deep-winter months of December, January and February (90 days) we had 36 with Highs of 0°C or more 40%, which is also about average.

For 5°C days we had 24, which is well below the average of 40. That was dragged down by the cold March & April.

Just in December-February we had 8 days hit 5°C, and that was actually still down from the average of about 13.

For 10°C days we had 4, which is well below the average of 12, and which again was dragged down by the cold spring. Although in recent years the winter of 2017-2018 only had 1 10°C from November 1st through April 7th.


That is it for a review of the temperatures for the "winter" of 2019-2020. All of these dashboards contain the data for Edmonton, as well as 8 other Canadian cities. We will be back in a week or two with the recap of the snow for the winter of 2019-2020.