Last winter we looked at
Edmonton's historic deepfreezes, including the epic, 26 days below -21°C that occurred in January of 1969.
Today we're going to switch to the more topical subject of summer heatwaves:
30°C Heatwaves
Edmonton's longest-ever recorded 30°C heatwave was 6 consecutive days, from June 2-7 in 1961, and the second-longest was 5 consecutive days in July of 1941. They're shown in this chart in red and purple respectively, with the background showing the more typical temperature distribution that we've seen for 1996-2017.
Since 1880 there have also been 10 other 4-day, 30°C heatwaves. That's too many to show on this chart, so instead only the two most recent ones - from August 2008 and July 2002 - are included. And even more recently, both July 2012 and August 2015 had 3-day streaks.
Edmonton has never recorded a solid week of days above 30°C though, so maybe that's too high a bar? Lets try 28°C instead:
28°C Heatwaves
Using 28°C as a cutoff instead, we have had two weeklong heatwaves: 7 consecutive days in July 1920, and 10 consecutive days in July & August 1984. There were also 7 other 6-day heatwaves, in 1906, 1917, 1933, 1936, 1941, 1961 (both of which we saw in the last chart) and 1981.
2015 is included in this chart because it had 3 separate 5-day streaks, in June, July and August.
Now we'll lower the bar one more time to 25°C:
25°C Heatwaves
Edmonton's longest-recorded stretch of days above 25°C was 16 days in 1984, and that was an extension of the 28°C heatwave that we saw in the last chart. The runners-up are 1915 and 1981 both with 15-days above 25°C in August.
And at just under two weeks, Edmonton has had 4 other 13-day streaks, in 1895, 1917, 1922, and then most recently in July 2007 which appears on the chart.
Warm Days Each Year
Looking at consecutive warm days is a bit arbitrary, because there could be a string of hot days which is broken up by one still-fairly-warm 24.5°C. It's fun for trivia, but in this chart we've switched over to comparing the total number of very warm days that each year had.
This chart shows the total number of days at-or-above 25°C, 28°C and 30°C, and as it cycles through them the 5-year averages appear as dotted, blue lines.
For 30°C days we average around 5 each year, although recently that has ranged from 0 in 2005, to 9 in 2015, to 13 in 2002. And 1961 is the all-time winner, recording 14 days (6 of which we saw in the first chart today).
For 28°C days the average is about 10 each year, although again there's quite a bit of variability. 2015 had 21, while 2010 only had 2. 1961 is again the winner, with 28, while 1916 was the only year to record 0.
(there were also two other years prior to 1900, but they're both missing quite a bit of data)
Finally, we average about 30 or 35 days at-or-above 25°C, from a warm year like 2015 with 52, to a cooler one like 2005 with 19. The all-time highest and lowest were 1898 with 64 and 1954 with only 10. The average has stayed pretty consistent over that last century though (as we've seen before, Edmonton isn't exactly getting hotter...it's more like we're getting less-cold)
2017 So Far
Here is where 2017 sits so far, compared to some of Edmonton's other, long 25°C heatwaves.
We are just at the end of a 6-day streak, and things are supposed to cool off for a few days, before warming up again later in the week. So far this year we've had 22 days at 25°C or above, 7 at 28°C or above, and 3 at 30°C or above (May 31, July 7 and July 9, all at 30.2°C). And we still have August and most of July left to go.
When we're in the middle of an Edmonton heatwave, it's always good to keep in mind that it will probably be brief.
