We won't be talking about smoke today, because I haven't found a source for historic air quality data. But after these past few days it is something that I'm going to research a bit more for the future.
High Temperatures
It was a bumpy May, with temperatures cool in the 1st week, warm in the 2nd week, fairly average in the 3rd & 4th weeks, and then there were a few really hot days near the end (and then the smoke arrived),
May 29th's High of 30.6°C set a warmest-since-1996 record, but was still below the warmest-since-1880 record of 32.2°C from back in 1936.
Digging into the numbers a bit more, May 2019's average High of 17.8°C was right on the average for May. In comparison, May 2018's average High was almost 5°C warmer at 22.3°C, which made last year the warmest May ever recorded in Edmonton.
May 2019 had one day which hit 30°C, with May 29th at 30.6°C. That makes 4 Mays in-a-row with days that hit 30°C, and since 1880 that had not happened before.
We had 2 Highs which hit 25°C which is close to the longterm average. It is well below recent Mays, though: 2018 had 13, 2016 had 7, 2015 had 6 & 2015 had 6. Our 11 Highs of 20°C was also about average, but below the 23 in 2018 and 18 in 2017.
And we didn't have any really cold Highs below 5°C, which happened most recently in 2014 & 2015.
May 2018
Just as a quick comparison, here we have May 2018 which was Edmonton's warmest May. Almost the whole month was well above average and was up near the top of the temperature range.
Low Temperatures
Low temperatures followed the same cold>warm>average>warm pattern, with a coldest-since-1996 Low of -4°C on May 5th, and a warmest-since-1996 Low of 12.4°C on May 12th.
The average Low of 5.4°C was just a touch below the 20-year average of 5.6°C. May 2019 had 5 Lows below freezing, compared to an average of 2.5, but we didn't have any Lows of -5°C.
Last Frost
Our final frost was on May 5th, which is two days earlier than the 30-year average of May 7th. In the past 5 years the final frosts have been May 5th in 2019, April 30th in 2018, April 28th in 2017, May 13th in 2016, and May 17th in 2015.
Warm & Cold Months
When we add up all of the Highs and the Lows the average temperature for May 2019 was 11.6°C, which is a little bit warmer than May's 20th century average of 11.1°C. That ranked 2019 as Edmonton's 58th warmest overall since 1880, and well below #1 2018 and #5 2017.
The average High of 17.8°C was Edmonton's 68th warmest, and the average Low of 5.4°C was the 51st warmest.
Looking at the 10-year average (dotted red lines) we can see that over the past century May's average High has crept up from 10°C to 11°C, while the average Low has increased from about 3°C to 6°C. We looked at this in more detail in The Months through the Years.
Our #58 May follows a #52 April and a #49 March, so the past few months have been quite quiet compared to our #5 coldest February, and #16 warmest January.
And here are all of the months for the past 20 years. March, April & May 2019 were all just a bit above average, so their orange bubbles are pretty small.
Precipitation
In May the International Airport received a total of 19mm of Precipitation (rain + snow), with Blatchford just below that at 17mm. That's well below the May average of 49mm, and below the 39mm that we got last year in 2018.
In recent years other low Mays at the International were 2015 with 17mm, 2011 with 16mm & 2002 with only 8mm.
So far for 2019 most months have had below average precipitation, and so our cumulative total for the year is pretty low.
The average total precipitation at the end of May (the white line) is 130mm, and so far the International (blue line) has had a bit more than half of that with 74mm, while Blatchford (green line) is at 49.5mm. And at this time last year (red line) we were at 114.6mm. June and July are our most reliably rainy months though, so our monsoon season will hopefully start soon.
Snow!
After the late-May heatwave it feels a little strange to talk about snow, but the month did start with a big snowfall, which carried over from the end of April. It was our 8th 5cm+ snowfall of the winter, and it was relatively late in the year for a big storm.
May 2019 recorded 5cm of snow, which is right on the average. Most months of the winter months were fairly close to the average, but December was about double the average, and September was snowier than anything we'd ever seen.
May's 5.4cm is pretty close to long-term average, but we only get snow in May about half of the time, and so a lot of those years get 0cm while others get 10cm+. The previous three Mays - 2016, 2017 & 2018 - had been snowless at the International, and 2019 broke that streak.
For the winter of 2018-2019 as a whole that brings the total snow to 160.6cm (blue line), compared to only 116.9cm for 2017-2018 (red line).
2018-2019's 160.6cm of snow ranks it as the International's 12th snowiest winter since 1960. But it is still well below some really snowy winters like 2002-2003 with 225cm at the International, or 1906-1907 with 239cm at Blatchford.
Remembering back to last fall, we had a very early first snow on September 12th. Then our first lasting snow arrived on November 1st, which was a little bit early. Then in the spring the snow melted down to 0cm again on March 31st, which was right about average. And finally our early May snowstorm meant that the final snow recordings at the airport were on May 4th. So:
- First snow to last snow: 235 days (7.8 months) from September 12 to May 4th
- First lasting snow to first big melt: 151 days (5 months) from November 1st to March 31st.
The winter of 2018-2019's 151 days with snow on the ground is not too unusual. It is about week longer than average, and it ranked as the International's 27th longest stretch.
The 235 days from first snow to final snow was pretty unusual though, ranking 7th longest at the International. Recently 2014-2015 was a week longer, at 241 days, while the long-term average has been closer to 200 days. The International's longest "winter" was 250 days in 1964-1965.
For June temperatures, it is typical for about half of the month to have Highs above 20°C, with maybe a week's worth of days above 25°C. In recent years 2018, 2016 & 2015 all had warm Junes, with almost 2 weeks of 25°C days. And Blatchford hasn't had a frost in June since 1942.
