September 2020 Review / October 2020 Preview

I think most people would agree that September 2020 was a pretty nice September in Edmonton, but just how nice was it?

High Temperatures

At the start of September our average daily High is 21°C, and over the course of the month things get cooler, and by the end of September the average High is 14°C. For September 2020 overall 23 days were warmer than the average, and 7 were colder. 

The end of the month seemed pretty warm, but in reality the High temperatures were only a little bit above the 30-year average, and they did not come anywhere close to the top of the range. But on the other hand, we also didn't have any really cold days down at the bottom of the range - which we did have in 2017, 2018 & 2019 (especially in 2018).

 

Looking at the numbers, September 2020 had a total of 15 days which hit 20°C, which is above the average of 10 days. That included one day which hit 25°C, with a High of 27°C on September 10th. On average September has 3 days hit 25°C, so we were actually a bit low this year.

September 2020 didn't record any Highs below 10°C though. That's a change compared to 2019 which had 4 Highs below 10°C (including 2 below 5°C), or 2018 which had 15(!) High below 10°C (including 7 below 5°C). The last September that didn't have any High below 10°C was 2016, and including 2020 that has only happened 8 times since 2000.

Low Temperatures

For the Low temperatures for the month 22 days were warmer than average and 8 were cooler. And similar to the Highs, the Lows were generally pretty far from the top or bottom of the range, although September 1st, 11th & 20th all came within about 0.5°C of the 30-year warmest Low.

Blatchford did not record any frosts in September 2020, although it came close on September 16th at 0.4°C. Most of the outlying stations did have at least one frost though, and the Airport had 3: on the 15th, 16th & 30th. The Blatchford station makes it through September without a frost about half of the time.

Warm & Cold Months

September 2020's average High of 18.7°C was above average, and ranked as the 32nd warmest September Highs since 1880. 

September 2020's Highs were a close match for 2017, and were warmer than 2014, 2015, 2016, 2018 & 2019. But going back a few years we had a series of really warm Septembers in 2009, 2011, 2012 & 2013 which all had average Highs above 20°C.

You can also toggle this chart to show the Lows, and September 2020's average Low of 7.4°C ranked as the 15th warmest September Lows since 1880. Over the past century September's average Low has increased from 2.5°C up to 6.4°C today.

In this chart each month since 2000 is represented a bubble, and the size of the bubble represents how much warmer or colder it was compared to the 20th century average for that month. Months which were warmer than the 20th century average are orange, and cooler months are blue.

September 2020's Highs were 1.8°C warmer than the 20th century average, and are an orange bubble. That follows the orange bubble for August at 1.2°C warmer than the 20th century average. But before that March-July 2020 were all either cool, or were right on the long-run average.

Looking across the country September was really warm in St. John's with an average High 3°C warmer than their 20th century average for September. And Vancouver, Edmonton & Calgary were all in the 1.6-1.9°C warmer range.

In comparison the central cities were all much closer to their 20th century averages. But it's worth pointing out that while Ottawa's average High of 19.8°C was -0.3°C below their 20th century average, it was still warmer than the "warm" September we had in Edmonton with an average High of 18.7°C.

Precipitation

In terms of precipitation this was a very dry September in Edmonton. September averages 33.4mm of precipitation, and Blatchford recorded only 5mm, which makes 2020 roughly the 7th lowest since 1880. The International recorded a bit more at 9.3mm, which was the airport's 6th lowest September since 1961.

Looking back over the year April was also extremely dry, but then May through August were all well above average.

For 2020 so far Blatchford has recorded 462.5mm of precipitation, and the International has 458.6mm. That is about 75mm above the average for this time of year, which is 386.2mm.

October Temperatures

For October temperatures, we have probably mostly seen the end of our 20°C days: October averages about 1 per month, but half of the time it doesn't have any. And we'll probably start seeing some below-freezing Highs, with October averaging 2 days below 0°C. For the Lows we will undoubtedly get our first frost, because October averages about 16 Lows above freezing.