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.


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. 


August 2020 Review / September 2020 Preview

What did we all think of August 2020? And how did the summer of 2020 compare? Let's find out.

High Temperatures

The late-July warmspell continued into the first week of August, followed by a week of slightly-below-average days, and then a few more hot days, and then we ended the month just on the cooler side of things. In total we had 13 Highs below average, and 18 above average. The warm days included two warmest-in-30-year Highs on August 2nd at 29.9°C and August 17th at 31.0°C.

Overall 26 days had highs which hit 20°C, when August's average is 23 days. That included 8 days at 25°C, compared to an August average of 9 days, and we had 2 days hit 30°C.

The end of the month felt a little chilly, and it was a little below average, but our coldest High was 16.6°C on the 30th. About half of the time August will have even colder Highs below 15°C, and 2002, 2004 & 2005 all had Highs below 10°C.

Hot Days

For the summer so far we have had 22 days hit 25°C. That's 2 more than the 20 which we had in 2019, but it is way down from the 34-54 which we had in the 4 warm summers from 2014-2018. The average is about 30 Highs at 25°C each summer, and so we were below that, and ranked as 107th out of 140 years.

We had 10 days hit 28°C, which is about average. That included 2 Highs at 30°C, which is below the average of 4 days. And for slightly milder days we have had 83 highs hit 20°C, which is basically right on the average.

Low Temperatures

The Lows started the month right at the top of the range, and then finished right at the bottom. Overall there were 12 Lows below average, and 19 above average. That included a warmest-in-30-years Low on August 2nd at 18.9°C, and a coldest-in-30-years on August 31st at 3.4°C.

Looking at the numbers, we did have one cool night below 5°C on the 31st, and those only happen about half of the time. Most of the Lows were between 10-15°C which is pretty typical for August.

Warm & Cold Months

August 2020's average High was 23.3°C, which was just above the recent average of 22.9°C and ranked as the 39th warmest overall. Over the years August's average High has stayed fairly close to 22°C.

If you flip the chart to show the Lows, August 2020's Low of 11.8°C ranked as 20th warmest. It was right on the recent average, but well above where things were a century ago when the average was around 8°C.

This chart shows the average High temperatures for each month going back to 2000. The bubbles represent how much warmer or colder each month was compared to the 20th century average, with big orange bubbles being much warmer, and blue bubbles being cooler.

August 2020's average High was 1.2°C warmer than the 20th century average for August, so it appears as a medium-sized orange bubble. That is the first notably orange bubble that we have seen since back in February, with March & April both notable cold, and May-July all right around the average. It also makes a difference from 2019, where the string of cool~ish months ran from May through October.

For the whole "summer" from May through August this ranked as Edmonton's 58th warmest, with an almost equal split between above-average and below-average Highs. In comparison 2019 was the 110th warmest, 2018 was 2nd warmest (after 1898 for some reason) and 2017 was 7th warmest.

Looking across the country the Highs for August 2020 ranged from right on the average in Ottawa and Vancouver, up to 2.6°C warmer than average in Calgary and 3.3°C warmer in Regina.

Monthly Precipitation

August's precipitation was above average at both Blatchford with 83mm and the International with 66mm. That is compared to an August average of 52.8mm, and it means that following an extremely dry April all of the summer months were above average.

For precipitation for the year so far the two Edmonton stations are very close, with Blatchford at 457mm and the International at 449mm. That is about 100mm above the for the end of August, which is 351mm.

A lot of Blachford's August rain came from one 33mm storm on August 3rd, which was the second largest of the year after 36mm on May 21st.

September Temperatures

For September Highs we still average 10 days at 20°C, including 3 at 25°C. Highs below 10°C only happen about half of the time, and in the last 20 years only 6 Septembers had a High below 5°C. But 2 of those years happened to be 2018 and 2019.

For September Lows, about half of the time September is frost-free, but we can see the below-freezing days creeping in as blue squares. September 2019 had 3 night with frosts, and 2018 had a ridiculous 8 of them.


July 2020 Review / August 2020 Preview

When you think back to the covid-summer of 2020, do you think you will remember the first 3 cool & rainy weeks of July, or the final hot one?

High Temperatures
The first few weeks of July 2020 weren't exactly cold, but there was a total lack of hot days.

The grey band in the middle of this chart is the 25th-75th percentiles for our High temperatures, which is where the temperatures will fall about half of the time. In the first part of the month July 1, 2, 7, 8, 12 & 13 were all below the 25th percentile and were pretty chilly for July. And only 1 day was actually above the 75th percentile into "hot" territory: July 16th at 27.1°C.

That all changed on July 27th when the temperatures finally (finally) jumped above average. They stayed there until the end of the month, and the forecasts say they will continue at least a little longer into August.

At the end of the month we finished with 17 days below average (including a 30-year coldest High), and 14 days above average.

In terms of the individual temperatures we didn't hit 30°C, but we did end up with 10 days at 25°C. That's below the July average of 12 days, but above years like 2019, 2011, 2010...

July 2020's average High of 23.4°C was on the cooler side of recent years, ranking as 12th warmest since 2000.

Hot Days So Far...
So far this summer we have had 14 days hit 25°C, which ties what we had last year in 2019. It's about 20-30 fewer than the very hot summers of 2015-2018, though. And it's a bit below the long-term average, which is about 20 Highs at 25°C by this point in the summer.

For slightly hotter days, we had our first 28°C High quite late on July 27th. We have now had 3 of those, while the average is around 6. And for milder 20°C days we have had 57, and that is below 2015-2018, but is pretty close to the long-term average.

Low Temperatures
The Low temperatures look a lot like the Highs, although at the end of the month we were right at the top of our 30-year range (and 0.1~0.2°C from the records).
The range of our July Low temperatures is usually very tight, and this year we had 4 nights below 10°C, 4 nights above 15°C, and everything else was between 10-15°C.

Warm & Cold Months
July 2020's average High of 23.4°C was just a bit below the recent average of 23.7°C and ranked as #67 our of 140. That average has stayed fairly level since records began in the 1880s, starting at 22.6°C, and rising as high as 24°C in the 1930s, and then dropping down to 22.4°C in the late 1990s.

July 2020's average Low of 12.9°C is right on the recent average, and ranks as #13 out of 140. While the July Highs have stayed fairly constant over the years, the average Lows have steadily increased from 8.5°C a century ago to about 13°C today.

Usually in these monthly reviews we talk about the mean temperatures (High & Low) of each month, but this is the middle of summer, and what people really care about are the Highs. So sticking with the Highs temperatures, in this chart the bubbles represent the average Highs for each month going back to 2000. These are compared to the 20th century average, and so big, orange bubbles were warmer than the 20th century average, and big, blue bubbles were colder.

You might notice that it has been a while since we have seen an orange bubble, because the last "warm" (above-average) Highs that we saw were back in February. Highs in March & April were both about 2°C below the 20th century average, and May, June & July 2020 barely show up here because they were so close to average.

So far during what we might call "summer" 2020 hasn't had any hot months, and it joins 2019, 2010, 2009, 2008, 2005, 2004 & 2000 which all had average-to-cool Highs for May through July. In 2019 that continued through August & September, and we didn't get another "warm" month until November. But hopefully August will turn things around for 2020.

Across the Country
Here we are taking a look at the Highs for July 2020 across the country, and there was quite a wide range. St. John's, Calgary & Vancouver were all 1°C or more below their 20th century averages, while Toronto, Ottawa & Montréal were 3.5~4°C above theirs.
This is a quick look at Toronto's Highs for July 2020. Their average High for the whole month was 30.3°C, which was the 2nd highest since 1880 (1921's average High was 31.2°C). Ottawa and Montréal are available in the dropdown on the upper right, and they look similar.

Monthly Precipitation
Heading back to Edmonton, and switching over to precipitation, in July Blatchford received 121.2mm which was its 27th rainiest July since 1880 (and below the 163.4mm in 2019). The International received 95.3mm, which was also its 27th rainiest, although those records only go back to 1960 (and it was also below the 118.6mm in 2019).

July's average precipitation is 90.8mm, so the International was just a bit above that, while Blatchford was above the 75th percentile and into the realm of "lots of rain." And looking at the chart June and May also both had lots of rain at both stations.

Blatchford's May-June-July total of 319.6mm was actually its 5th highest since 1880 (1901 leads with 410.4mm). The International's 310.1mm was its 3rd highest May-June-July since 1960 (2010 had 332mm).

Days With Rain
July averages 15 days with rain, and in 2020 Blatchford recorded 17 days while the International had 20. So it was not as rainy as it might have seemed. July is usually our rainiest month, and from mid-June through mid-July is our little monsoon season.

Precipitation So Far...
For 2020 so far the International has recorded 383.8mm of total precipitation (rain + snow), and Blatchford is just a bit below that at 374.5mm. The average for this time of year is 300mm, so we are definitely above average, and things really took-off in May, June & July after our very dry April.

August Temperatures
For August the daytime Highs are above 20°C most of the time, with typically about 25 warm days each month. We also average a week or two of days above 25°C, but 30°C days only happen about half of the time in August. For the Low temperatures it should be a lot of the same 10-20°C orange which we saw for July, but with a few more nights in the 5-10°C range, and every 5 years-or-so a night below 5°C. And also, August's average precipitation is about half of July's.

August 2019 was pretty blah, but that followed a string of warm years from 2011-2018. So hopefully last year was the anomaly, and summer 2020 actually hangs around for awhile this time.


Whitemud Creek and Sturgeon River

Today, something that is probably only of interest to me and handful of other people: we have a dashboard for the river levels in Whitemud Creek in Edmonton, and the Sturgeon River in St. Albert.

This dashboard shows the most recent readings from some of the stations around Edmonton. If you hover over each of the dots a graph of the recent depths and streamflows will appear.

Why are the depths and streamflows interesting?

Whitemud Creek and the Sturgeon are both paddleable throughout the spring and summer...but that is dependent on the water levels.

The province provides the data at https://rivers.alberta.ca/. That is a great site with some basic charts, and it provides near-realtime updates. But for data as spikey as creek levels average and quartiles don't give the whole context.

So this dashboard pulls the data from https://rivers.alberta.ca/ once per day, and it shows the daily maximum & minimum streamflows for all of the available years.

(A note about the depth for the Whitemud Creek at Rainbow Valley: it's waaaaay too high. I don't know what datum is being used, but the number never drops below 5m, and that is completely incorrect. I had thought that maybe it was measured relative to the same datum which is used for the North Saskatchewan, but that is not the case either. In a flood state like we just had the river measured 8m while upstream the creek depth was only at 6.6m.)

Late Summer
In the spring the water levels are reliably very high, but through July, August and into September they are generally quite low with occasional bumps from storms. 

With the government site it is difficult to know exactly what to expect later in the season, and so this chart shows how often the levels are high later in the season. And late-season spikes are common throughout July & August, but they only last about 3~4 days before the levels return to normal.

The Sturgeon
The data for these stations only goes back 10~20 years, and so there isn't a huge history. 

But just for some trivia, so far in 2020 the Sturgeon has been very high with a depth close to 2m and streamflow of 15m³/s. More typically in July the depth would be below 1.5m and the streamflow would be under 5m³/s. And in this chart if you click on the line for 2019 it was very high in August with a depth of over 2m and streamflow of 10m³/s.

This dashboard is definitely a niche interest. And if you need realtime data the https://rivers.alberta.ca/ site is a much better source. But for a more granular history and some context this dashboard can be handy. If you do find this dashboard useful the fullsize version here is probably better than the one embedded in this blogpost.