2021/04/11

April 10 2021 - Spring Snow

It happened: on April 10th we had a nice, big, spring snowstorm. Hopefully everyone enjoyed all of the "second-winter" Hobbit jokes, but how unusual are April snowstorms?

April Snow
In April on average we get about 15cm of new snow. The last time that we had a snowless April was 2005 at Blatchford, or 1998 at the International Airport.

In May we average another 5cm. That can vary from snowless Mays like 2016-2017 and 2011-2013, to 2020 with 4cm, 2015 with 12cm, 2010 with 28cm or all the way to May 2003 with 38cm.

Blatchford doesn't record snowfall anymore, but on April 10, 2021 the International recorded 4.2cm of snow. If that is all the snow that we get during this month then this April would be a bottom-20 year at the International.

But when do we typically have our final snowfall for the year?


Final Snow
If this April 10th storm really is our final snow for the year it would be the earliest final snowfall at the International since 1998.

I'm sure that no one really wants to hear this, but from the past 10 winters the average date of the final snow is...May 1st. (this chart shows the 10-year average as April 25th because it's including 2021's April 10th in the calculation, but without 2021 it falls back to May 1st.)

In both 2020 and 2019 it was on May 4th, in 2018 it pretty early on April 16th, and both 2017 and 2016 were April 24th. And then a year like 2011 was really late on May 13th.


Spring Snowstorms
Our April 10th storm was 4.2cm, and so for comparison this chart shows every 4cm+ storm for April and May. This year's storm is the small~ish bubble furthest to the right.

Large April storms are pretty common, and they might drop-off a little bit after mid-April, but they don't really disappear until after the first week of May. And even then sometimes we will get big storms in mid-May, or even in late-May like the 7.8cm we got in 2010 on May 29.

So enjoy this second-winter. But keep in mind that there could be a third or fourth yet to come.

2021/04/01

March 2021 Review

Today we are going to take a look back at the weather for March 2021.

We will talk a bit about the winter in general too, but if you are interested in how the winter of 2020-2021 compared overall we had a detailed look at it a few weeks ago in 2020-2021 Winter In Review: Temperatures.




March 2021 High Temperatures
Here we have the High temperatures for March 2021. We ended up with 5 Highs which were colder than the 30-year average, compared to 26 which warmer. And that included 2 warmest-in-30-year Highs on March 17th at 12.6°C and March 18th at 15.8°C. 

One of the cruel tricks of Alberta weather is that the start of March was warmer than the end. We jumped from "winter" to "spring," and it felt let we were on the way to "summer," but unsurprisingly the real summer is still many months away. The end of the month certainly felt a lot colder than the start did, but it was all pretty typical for March.

Looking at the numbers we only had 2 Highs below freezing, compared to an average of about 11 for March. On the other end we had 10 Highs above 10°C, when March averages about 4. And that included 1 High above 15°C, which in recent years had only happened in 2019, 2015, 2010 and 2004.
 

March 2021 Low Temperatures
For the Low temperatures we had 8 below average, compared to 23 above. And that included 3 warmest-in-30-year Lows, including a new record-warmest Low of 3.9°C on March 14th.

Our coldest Low this month was -14.1°C on March 14. In total we had 3 Lows below -10°C, while March averages 10. The only recent Marches which didn't hit -15°C were 2010, 2016 and now 2021. March 2017-2020 all hit -20°C at least once, with 2019 having 3 Lows which dropped below -25°C.
 

Warm and Cold Months
So overall March 2021 was a pretty warm month. 

Its average High ranked as 5th Highest, and 5.8°C warmer than March's average. It was the warmest March Highs since 4th place 1988, which was just tiny bit warmer. Before that we need to go back to 1910, which is in 1st place with an average High of 10.7°C. 

The Lows weren't quite as unusual, ending up in 14th spot at about 3.5°C warmer than average. Recently March 2016, 2015 and 2010 all had warmer average Lows.

In this chart orange bubbles represent months where the Mean temperature (the average of the Highs and the Lows) was warmer than the 20th century average, while blue bubbles were colder.

March 2021 is a fairly large orange bubble at 5.8°C warmer than the 20th century average. That is about the same size as March 2016 and a little bit bigger than March 2015. It follows a cool February and a warm January this year.
 

Across Canada
Looking across Canada it was a warm March in all of these cities, but especially on the prairies. Winnipeg was at the top at 6.8°C warmer than its 20th century average temperature for March.
 

2021 So Far
In this chart the red line shows how the temperatures each day compared to the average temperature for the 20th century. When days were above-average days the line goes up, and for below-average days it drops. 

After 3 month of 2021 we have had Edmonton's 25th warmest start to a year. Things got off to a really warm start in January, but the red lines all take a significant dip for the coldsnap in late-January and early-February. But after that things start climbing again through March.

In this chart each of the bars represents the average temperature for January-March compared to the 20th century average for each of these cities.

Looking across the country again, most of the cities here have had a top-25 warmest January-March, with Toronto, Calgary and Vancouver as the exceptions at around the 40th spot.
 

Snowfall

The International Airport recorded 5.5cm of snow in March, which is below the average of 19cm. This winter February's snow was right on the average, November's was above, and all of the other months have been low.
 

For the winter so far we have had 68.3cm of snow, which is well below the average of 100cm for this point in the winter. But, in April and May we do average another 20cm of snow, so the snow season probably isn't over.
 

This chart has the snowfall totals for cities across Canada. It is a little tough to read, but out 68.3cm of snow just pushes us above Winnipeg's 66.2cm. Next is Toronto at 100cm. Calgary, Ottawa and Montréal are all from 138-164cm, and St. John's is up at 282cm.

Most of these numbers are within the typical ranges for these cities. The biggest outliers are Edmonton and Winnipeg which are quite low, while Calgary's 138cm is above its average of 112cm.
 

Snowdepth
In terms of snowdepth, the warm temperatures at the start of March gave us an early melt. Blatchford's last recorded snow was on March 9th, and the International's was on March 20th. But then the International did pop up to 4cm with some fresh snow on March 29th.

And across Canada the warm March meant that all of these stations were snow-free by the end of March.
 

April Temperatures
For April temperatures on-average it only has 3 Highs below 0°C, and about three-quarters of the time April will have a day hit 20°C. 2001, 2015, 2016, and 2018 all had days hit 25°C.

In recent years April 2020 and April 2018 both started quite cold though. We hadn't had a -20°C Low in April since 1982, but April 2nd 2020 broke that streak hitting -20.8°C. More typically though, only about one-third of recent Aprils had any Lows which hit -10°C.

We almost certainly haven't seen the end of the snow though, because in April and May we average another 15cm and 6cm of snow respectively.

2021/03/28

Zero Snowdepth for 2021

This is a little late, because after a warm start to March things have cooled off a bit, and that threw some uncertainty into the question of whether our snow has officially melted or not.


2020-2021 Snowdepth
In this chart the blue and orange lines are the snowdepth for the winter of 2020-2021 for Blatchford and the International respectively. The light blue stuff in the background shows the average and the range of snowdepths at the International over the past 30 years.

Blatchford's final recorded snowdepth this winter was on March 9th at 3cm, and after that snowdepth has been blank. The International hit 2cm on March 17th, and it hung out there until March 20th. On the 21st it had no meausurement, and since then it has been showing "Trace" amounts of snow on the ground. "Trace" doesn't mean 0cm, but it's close, and eventually it will disappear.

For the winter as a whole both stations jumped to well above average in early-November, and then were mostly flat through mid-February. Things started to drop in the last week of February, and then really fell off a cliff in the first week of March.


2020-2021 Snowdepth - Outlying Areas
For a bit more context, here the snowdepths for Stony Plain and Campsie (about 100km NW of Edmonton) are also shown.

Snowdepth seems to be Environment Canada's least precise measurement, but the Stony Plain and Campsie stations had less snowdepth for most of the winter than the two main Edmonton stations did. Stony Plain's snow disappeared about a week before Blatchford on March 2nd. For Campsie it was March 15th, which was a week after Blatchford and a week before the International.


Recent Winters
This chart has the history of snowdepths and melts for recent winters.

March 21st is pretty early for all of these stations to be snow-free, although 2015 and 2016 were both about a week earlier. But comparied to years like 2020, 2018 and 2013 this winter was about a month ahead.

People always like to joke about "second winter," and just because all of the snow has melted that doesn't mean that we won't get more. In April and May we average another 20cm of new snow, but looking at the snowdepths here that late-spring snow usually doesn't have much of an impact on the ground. 2015 and 2016 both had early melts, which were followed by another week of snow in late-March. And winters like 2017 and 2014 had fairly late melts, and after that the snow showed up again for another week in mid-late April.


Lasting Snow
In this chart each of the narrow blobs shows the length of time for which there was snow on the ground during each winter.

For the winter of 2020-2021 Blatchford had snow on the ground for 122 days in-a-row. That was from and early~ish start on November 8th through to the early finish on March 9th. In recent years 2019-2020 went 141 days and 2017-2018 went 170, while 2014-2015 went 95.

The International had measureable snow on the ground (we ignore the "trace" amounts in the chart) for 133 days, from November 8th through March 20th. 133 days is pretty low for the International: 2016-2017 went 134, 2015-2016 went 121, 2014-2015 went 126. For longer winters recently 2019-2020 was up at 169 days, with 2017-2018 at 172.

2021/03/21

2020-2021 Winter In Review: Temperatures

Spring is here, at least according to the calendar. That means that it is time to take a look back at the winter of 2020-2021. However, in Edmonton "winter" definitely does not begin on December 21, and so we will be looking at is the period from November 1st through March 20th. 

Daily High Temperatures

The thin grey line in this chart is the 30-year average High, and November makes a nice start to "winter" because the temperatures in early November mirror late-March. At the start of November our average High is around 4°C, that falls to -8°C by the time winter officially starts in late-December, and then by late-March it's back around 4°C.

For the winter of 2020-2021 then:
  • November when from a really warm start, to just below-average for two weeks, to back above average.
  • December was well above-average, except for a few cool days from the 11th through 17th.
  • January was also well above-average, until temperatures dropped on January 23rd.
  • February started below-average, but then dropped into the coldest-in-30-years range from the 6th through 14th. It bounced back up starting on the 19th, though.
  • Early March was mostly well above-averarge, with the 10th dipping just below average.
In total we had 88 Highs above-average, including 7 which were the warmest-in-30-years. And that compares to 52 below-average days, including 6 that were the coldest-in-30 years (and were all from February 8-14).

"Warm" Winter Days

From November 1st through March 20th is 140 days, and during that time we had 73 days with Highs which hit 0°C, or 52% of the time. That's above the average of about 64 days, and it is the most since the winter of 2015-2016 which had 81.

Included in that were 40 days which hit 5°C, or 28% of the winter. The average is about 30 days, and this was the most since 2004-2005 which had 42.


This winter did have the distinction of going 29 days in-a-row without a High that hit 0°C, and that was from January 21st through February 18th. The record was 82 days from November 11th 1955 through February 1st 1966, and compared to that our 29 days is not very impressive. But 29 days was the longest since 2011 with 38 days, and it was about a week longer than the typical 21 days that we get each winter.

Daily Low Temperatures

Here are the Low Temperatures for the winter, and they look similar to the Highs with the big coldsnap of late-January through mid-February really standing out, while everything else was quite mild.

We had 85 above-average Lows. That included 7 which were the warmest Lows in 30 years, and March 14th set a record warmest Low at 3.9°C. In comparison there were 55 below-average Lows, including 2 coldest-in-30-years Lows on February 8th at -31.6°C and February 11th at -28.9°C.

Cold Winter Days

Looking at the very coldest days this winter we had 22 Lows hit -20°C, compared to an average of about 25 each winter. The first one was on December 18th, and then the other 21 were all crammed into roughly a month from January 23rd through February 17th.

Included in that were 8 Lows at -25°C, all from February 6th through February 14th. We average about 11 of those each winter. 3 Lows hit -30°C, all in a row on February 7th through 9th. And February 7th was the coldest Low of the year at -33.9°C.

The Horserace

In this chart the red line shows how the temperatures each day compared to the average temperature for the 20th century. When days were above-average days the line goes up, and for below-average days it drops. 

For the start of the winter in November things were fairly flat, but starting in December the lines really started to climb through late-January. The deepfreeze in late-January and February pushed things down for a few weeks, and then they recovered again with the warm March.

As of March 20th this was the 17th warmest November 1st through March 20th, with the Lows as the 16th warmest and the Highs in the 18th spot. During this winter we averaged about 3.2°C warmer than the 20th century average.

If you change the timeframe for this chart to December 1st through March 20th this was the 13th warmest winter, at about 4°C above the 20th century average.

Across Canada

Here we have the relative temperatures for November 1st through March 20th, compared to the 20th century average, for 9 cities across Canada. There are based on the mean daily temperatures (the average of the High and Low), but the High or Low can be selected from the dropdown on the lower left.

As we saw, for Edmonton this was the 17th warmest November 1st through March 20th, and Calgary and Regina were in roughly the same spot. Toronto and Vancouver were both down around #25. For Ottawa and Montréal it was the 10th warmest, for St. John's it was #8, and for Winnipeg it was way up at #7.

Warm and Cold Months

Breaking things down by month the cold February (shown here as the big, blue bubbles) wasn't just in Edmonton, but stretched from Vancouver through Toronto. On the other hand the prairies had a very warm March, while in central Canada it was fairly average.

For November through March for these 9 cities the only below-average months were February for Vancouver through Toronto, and March was just a tiny bit below-average for Ottawa and Montréal. Everything else was in the orange, and generally well above-average.

Warm Winter Days Across Canada

This chart shows the number of "mild" days with Highs of at least 0°C for each Canadian city from November 1st through March 20th. Unsurprisingly Vancouver blows away the competition, with just about every High above freezing. Toronto is next with an average of about 100 days, and Calgary and St. John's are both around 85. Montréal and Ottawa average around 75, with Edmonton at 65. Regina is down at 50, and finally Winnipeg averages 38.

Taking it one step further to 5°C Vancouver is again at the top, with only about a week or two each winter which doesn't hit 5°C. Calgary and Toronto next, both averaging around 50 Highs that hit 5°C from November 1st through March 20th. Edmonton, Ottawa, Montréal and St. John's all average around 30. And then Regina and Winnipeg are around 15.

Cold Winter Days Across Canada

For -20°C Lows each winter Vancouver doesn't even show up, and St. John's hasn't had one since 1994. Toronto might get anywhere from 0-10, for Montréal it is 3-20, and Ottawa it is 5-40. Average are tough though, because each year is all over the place. The prairies are more predictable though, with Calgary averaging around 20, Edmonton around 24, Regina around 40 and Winnipeg around 50. 

For -25°C Lows each winter it is basically just the prairie cities, with Calgary averaging about 8, Edmonton 9, and Regina and Winnipeg at 24. Ottawa also averages around 6, but that bounces from 0-10 each winter.

That brings us to the end of our look back at the temperatures for the "winter" of 2020-2021. Once the snow at the International hits 0cm we will do a recap of this winter's snow.