2017-2018 Winter in Review - The Really Cold Days

Today is the first official day of "spring," but this is Edmonton, and we shouldn't fall into the trap of expecting summer to suddenly appear. We will still probably have snow on the ground until mid-April; about half the time we will get some new snow in May; and things won't turn green until mid-late May.

But the good news is that by this point in the year we've probably seen the last of the winter's really cold days. The last time that we had a temperature of -20°C in April was 1982, and then 1975 and 1954 before that. And even -15°C in April is pretty unlikely, most recently happening in 2002, 1992, 1982 and etc.

In the next few weeks we'll be doing a full 2017-2018 Winter-in-Review, and today we're going to get a head-start start by looking at the really cold days that we've had over the last few months. How did this winter compare to other recent years?

Low Temperatures So Far

Here is a reminder of our Low temperatures for the last few months. November started really cold, December started really warm and ended really cold, January bounced around a bit, February was mostly pretty cold, and now March has been pretty average.

The Really Cold Days

Here we have a count of the really cold days for this winter, as well as for the last 10 winters going back to 2007-2008.

This winter we had a total of 30 days below -20°C, including: 19 days between -20°C & -25°C, 8 between -25°C & -30°C, and then 3 more days below -30°C.

Prior to this winter, the last time that we'd had a -30°C was on January 4, 2015. That streak came to an end on December 29, 2017 with a Low temperature of -30.7°C. It had lasted 1,089 days which was a week shy of 3 years. Edmonton's longest stretch without a -30°C was 1,835 days from January 13, 1998 through January 3, 2003.

We had 2 other -30°C days this winter, at -30.5°C on December 12th and -30.7°C on February 4th. The last winter with 3 or more days below -30°C was 2009-2010, but that winter included a -36.7°C on December 13th. Right now it's been about 3,020 days since we last hit -35°C, and that is the longest that Edmonton has ever gone. The previous record was 2,556 days from 1997 to 2004.

Here's another version of the same data:

This is exactly the same data, and personally I prefer the first chart, but this one does make it easier to compare the totals for each year.

2017-2018's 30 days of -20°C was less than the 39 in 2008-2009, the 46 in 2010-2011, and the 37 in 2013-2014, but it was more than any of the other winters here.

Coldsnaps

When we get really cold days they often come in packs, and this chart shows how the -20°C and -25°C days were grouped together this winter.

Our longest stretch of Lows that were -20°C or colder was 9 days, from Christmas Eve through New Year's Day. And we had another 7-day stretch from January 31st through February 6th. The only other 9-day stretch shown here was in December 2010, so that's pretty uncommon. Going back a bit further in January 1998 we went 15 days below -20°C, and January 1996 went 23 days.

For Lows of -25°C or colder we had a 5-day stretch just before New Year's. That was a longer coldsnap than any of the other years shown here, but it was nowhere near Edmonton's longest recorded coldsnap in January 1969 which had Lows below -25°C for 26 straight days.

Highs Below -20°C

During this winter we also had 6 days with High Temperatures below -20°C, which was more than any winter since 2010-2011 which had 12. This year they came in two groups of 3, the first during the Christmas coldsnap, and then again in mid-January. In the last two winters we hadn't had any Highs below -20°C.

Commutes

Now we're going to go back to where this blog all began, as we estimate how many really cold Monday-Friday commutes there were this year.

If you walked, biked, or took transit through this winter you survived roughly 24 trips (AM & PM) at -20°C or colder, including 7 from -25°C to -30°C and 1 below -30°C. That was more than the last 3 winters, especially the two mild el niño winters of 2014-2015 and 2015-2016, and it was about 1 cold trip less than 2013-2014. The real standout here was 2010-2011, with 46 trips or almost double what we had this winter.

1880-Today

And here we have a longer-term view of how things have changed over the years.

Right now we average about about 23 days below -20°C each winter, and so the 30 days that we had this year was a bit high. But in the 1880s the average was up over 50 days, and in the 1960s it was around 40 days, so we can't complain too much?

1980-Today

When we just focus on "recent" history going back to 1980, the changes haven't been quite so dramatic.

Since 1980 the average number of days that hit -20°C has bounced around between 20-30, and there was a nice little lull from about 1998-2008. Days that hit -25°C has slipped from an average of about 15 down to 8, and we haven't had 20 -25°C days during one winter since 1995-1996. And -30°C days have crept down a bit too: in the 1980s we had a total of 30, for the 1990s it was 37, in the 2000s it was 18, and so far in the 2010's we've had 11 (with 2 more winters to go, and an average of about 1 per winter).