May 2021 Review

It's time for our look back at May 2021. This one will be a little long, because this month had a bit of everything.

High Temperatures

May 2021's High temperatures were probably the least interesting part of the month, with 13 Highs below average and the rest above.

We didn't have any scorching hot days, or any days that were really, really cold, although the 8th, 19th and 20th did dip down near the bottom of our 30-year range.

On average in May we have about 10 days with Highs which hit 20°C, and in 2021 we were just a bit above that with 11. 

May also averages around 2 days which hit 25°C, and 2021 didn't have any, although the 30th came very close at 24.6°C. In recent years the only Mays which didn't hit 25°C were 2021, 2011, 2009, 2005, 2000 and 1996.

We had 3 days with Highs below 10°C, which is right on the average for May. Our coldest High was 5.6°C on May 20th. The last time that we had a May day with a High below 5°C was 2015.

 

Low Temperatures

The Lows were a little bit more interesting than the Highs. A record warmest Low of 13.4°C was set on May 16th, and then 2 days later temperatures plunged down to near the bottom of the 30-year range for the 18th through 21st, and that included 2 late frosts on the 20th and 21st.

Frost in May is fairly common at Blatchford, and will happen about half of the time. But that frost usually comes early in the month, and after May 15th Blatchford is usually "fairly" safe from frost. But that didn't happen this year, with frosts on May 20th and 21st, which were the latest frosts that Blatchford had seen since 2009.

 

Final Frost

Around the region Blatchford and Stony Plain both recorded their final frost on May 21st, which is several weeks later than their average.

For the International Airport and Campsie right now the final frost was on May 22nd, and that would actually be early for both of those stations, although at those stations there's always a chance of a later frost coming in June.

For some of our prairie neighbours, assuming that things don't cool off again then Calgary and Winnipeg had their final frosts right around their average, while Regina's was a week and a half early.

 

Warm and Cold Months

May 2021 wasn't cold, but it wasn't particularly hot either. Its average High of 16.9°C ranked as only our 96th warmest since 1880, while the average Low of 5.2°C was 56th warmest.

In this chart months which were warmer than the 20th century average are orange bubbles, and cooler months are blue.

...May 2021 is a tiny bubble here, because it's overall temperature matched May's 20th century average.

Recently May 2018 & 2017 were warm, while 2014, 2010 & 2011 were cool.

For 2021 so far we've had a warm Jan, cold Feb, warm Mar, slightly warm Apr, and an average May.

May 2021 shows up as a tiny little bubble here, because its overall temperature was a perfect match for May's 20th century average. Recently May 2018 and 2017 were above average, while 2014, 2010 and 2011 were notably below.

So far for 2021 we've had a warm January (relatively), cold February, warm March, just slightly warm April, and an average May.

Looking across Canada May 2021 was average~cool in Vancouver and the prairie cities, and warm-ish in the cities in Ontario and Quebec, as well as in St. John's. Montréal had the largest difference at 1.3°C warmer than its long-term average for May.

 

Snow

So yeah, we got snow in May, with the International recording 9cm. That's about double May's average of 5cm.

About half of the time May doesn't get any snow: recently May 2021, 2020, 2019, 2015 and 2014 all had some snow, while 2018, 2017, 2016, 2013, 2012 and 2011 were snowfree.

While May gets some snow about half of the time, the average date of our final snowfall is April 29th. 2021's final snow on May 19th was several weeks after the average, and was the latest snowfall since 2011's June 4th. 

Our first snowfall of the winter was back on October 16th, and so the winter of 2020-2021 went 216 days (7 months) from first to final snow, and that is right around average.

It wasn't only Edmonton with May snow, because Calgary recorded 7.8cm and St. John's had 3.6cm. (Regina and Winnipeg also maybe got some snow, but Regina doesn't record snow anymore and Winnipeg's snow records are a little spotty)

For the winter overall the airport recorded 82.5cm of snow. That was well below the average of 125cm, and ranked as the airport's 10th least-snowy winter, going back to 1960.

This chart is always pretty messy, but it shows the cumulative snow totals for other Canadian cities for the winter of 2020-2021. Vancouver is predictably at the bottom with 12.6cm. Winnipeg was next with 66cm (a combination of a truly dry winter, and spotty measurements), and then Edmonton is next with its 85cm. St. John's was at the top with 289cm.

 

Precipitation

Along with the late snow we also had a fair amount of rain in May 2021. May averages about 52mm of combined precipitation (rain + snow), and Blatchford, Stony Plain and the International were all about that.

The International had the most with 91.2mm, which was its 7th rainiest May on record, and just a bit below 2020's 97.5mm.

We had had a very dry start to 2021, but the above-average precipitation in May has pushed the International up to a total of 132mm, which is right on the average for the end of May. Blatchford and Stony Plain are still below average, but they aren't cruising along the very bottom of our typical range like they were a month ago.

Even though the total precipitation in May was above average, the number of days with precipitation wasn't unusual. 

In May we average 11 days with precipitation, and Stony Plain and the airport were right around average, while Blatchford was a little low. As we head into summer we are also heading into our rainy season, with June and July both averaging around 15 rainy days. 

The bubbles at the bottom of this chart show the individual precipitation events, and the International had a really large 45.8mm day on May 18th, while Blatchford and Stony Plain peaked at a little below 30mm.

45cm of precipitation in a day is a lot for Edmonton, and this chart has the history of 45cm+ days for the International going back to 1960. 

The last time that it happened was July 25, 2014 with 46mm of rain, and before that July 29, 2001 with 57mm.

May 18th's storm was the earliest 45cm day recorded at International, because normally when we get that much precipitation it will be during a summer thunderstorm. The next earliest was June 15, 1973.

 

June Temperatures

As we head into June usually about half of the month has Highs above 20°C, and there is also maybe a week of days above 25°C. For Low temperatures the last time that Blatchford had a frost in June was way back in 1942. The last time that June had snow was 2011, so it's not impossible, but it has only happened in 2011, 1967, 1922 and 1888.