Warmspells

Last week in Edmonton we had a nice, little, don't-call-it-a-chinook. It melted a lot of the snow (not that we've had very much this winter), and we got close to a few records, but as I've said, it wasn't particularly unusual. And although the temperatures have cooled off a bit this week, the forecast is predicting that we'll be up above freezing again soon.

A few weeks ago we'd looked at our winter coldsnaps - how often they happen, and how long they last. Today we'll do the same thing for our mid-winter warmspells.

Winter High Temperatures

Here is a chart of daytime high temperatures for the last 6 winters - the oranges are temperatures above freezing, and the blues are below. I'm going back to 2010-2011 with this because we've seen that it was a particularly cold winter, especially compared to 2015-2016 which was very mild.

So far for 2016-2017 we've had a very warm November, but then most of December and January were fairly cold. We've only popped up above freezing for a few days in December, and then again last week.

Highs Above 0°C

Here the days above 0°C are highlighted, and I've added numbers to count the length of each warmspell:

• A lot of these warmspells are only 1 or 2 days long, so the labels get pretty cluttered. To clean that up I've animated it, which hopefully makes the longer warmspells a little bit easier to spot.
• I haven't counted the lengths of any warmspells that are right at the start of November or the end of March, because that's really the point were we're transitioning into and out of winter.

The 7-day warmspell that we just had was fairly typical, because each of the last 6 winters has had at least one 5ish day warmspell in January or February. The winning mid-winter warmspell was 2014-2015 with a 12-day streak at the beginning of January. And by the time we move into March streaks of 10 or 15 days become more common.

We can also see how the years vary in terms of warm days. Of the roughly 150 days from November through March, 2011-2012 and 2015-2016 both had 90 or more days above freezing, 2010-2011, 2012-2013 and 2013-2014 were all down around the 50-day mark though, and 2014-2015 had 72.

Highs Above 5°C

In the middle of the winter any day that's above freezing can be nice, but we don't get much melting unless we're above 5°C, so that's what we're looking at here.

Again we see a lot of 1 and 2 days streaks spread throughout the winter. The 4-day streak that we just had is a little on the long side of things, but every year here except for 2012-2013 had a 3 or 4 day streak in January or February. And of the 33 winter months that are shown here, there were only 4 that had no days above 5°C: December 2010, December 2012, February 2014, and December 2016.

Normally the theme of this blog is something like "Edmonton's winter: it's warmer than you think." And while I do generally believe that sentiment, it is a little interesting to see 2012-2013, and to realize that for 5 entire months there were only 16 days that actually broke 5°C. That's on the low side of things compared to the other winters, but still. Our December-February really isn't that bad, but a cool November and March can sure make things long.

When looking at winter I'm never sure if I should use November and March or not, but I wanted to include them here today because I'd also used them when looking at coldsnaps:

Warmspells and Coldsnaps

So here we have a comparison of our warmspells (High above 0°C) and coldsnaps (Low below -20°C). And for the most part we do have a lot more days above 0°C than below -20°C. Although the cool winter of 2010-2011 did come very close to parity.

Time Between Warmspells

Finally for today, we'll take a look at how long we have to wait between warmspells.

This chart shows the longest gap in each winter without a day above freezing.

In 2010-2011 we went 38 days - from November 27 through January 3 - without a high of 0°C. And at the shorter end of things, in 2011-2012 we never went more than 8 days without a high of 0°C.

More typically, in each winter there will be at least one 2~3 week stretch where the temperatures don't warm up to freezing.

For the sake of trivia, Edmonton's longest-ever recorded stretch of days that didn't reach 0°C was 83, from November 11, 1955 through February 1, 1956.

And here we have the longest gap each winter without a 5°C day.

In the deepest, darkest depths of winter we might sometimes wait 2~3 weeks for a 0°C day, but for 5°C it's more like a month-and-a-half. Again, this just shows the longest gap each winter, and there are certainly shorter ones as well. But for each of these winters except 2011-2012, there was at least one extended period without 5°C - usually in late-November through early-January.

Edmonton's longest-ever recorded stretch of days below 5°C was probably 116 days, from November 8, 1978 through March 3, 1979. I say "probably" because there are two stretches in 1887 and 1993 that might be contenders, but they're both missing quite a bit of data. In recent memory, November 13, 2007 through February 14, 2008 was a 93-day stretch where the temperature never reached 5°C.