April Review / May Preview

It's the end of the month, so it's time to look back at a weird April.

A caveat for today: Environment Canada's daily data for Blatchford is missing from April 21st onwards. They still have the hourly data, and that is generally fine, but it doesn't capture the very highest or lowest temperature each day, so it isn't great for things like records. This isn't ideal, but we'll make do.


High Temperatures

April started out really cold, as the late-March coldsnap dragged on for two extra weeks.

We actually set a record for all-time coldest High on April 5th at -8.8°C, and we also set 3 other recent (since 1996) coldest Highs on April 6th, 11th and 12th. And then at the end of the month we set a recent record for warmest High on April 28th at 27.5°C, which was still about 2°C below the all-time record of 29.4°C from 1939.

What a weird month.

The average High was 7.4°C, which was just a bit below the 7.6°C from last year. But we got there by having 9 Highs below 0°C (which tied 2002) including 3 Highs below -5°C (which tied 2008). And then in the last week of the month we had 3 Highs above 20°C (which is pretty high), including 27.5°C on April 28th, which was Edmonton's warmest April day since April 16th, 1984 at 28.1°C.


Low Temperatures

The Low temperatures were similar to what we saw for the Highs, with 3 recent coldest-Lows in the first week of the month. And then at the end of the month the 7.1°C Low on April 28th was just a touch below the recent record of 7.2°C for that date.

Looking at the numbers this April had more Lows below -15°C and below -10°C than any other recent April. The average Low of -3.3°C was the third coldest of these years, behind 2013 at -3.5°C and 2002 at -5°C.


2018 Temperatures So Far...

Before the late-April heatwave people were getting pretty grumpy with our forever-winter. But how does 2018 rank, so far?

This chart compares temperatures on a day-by-day basis to the 20th century average. 2018 is shown as the animated red line, and lines for the last 10 years are shown for reference.

At the beginning of March, 2018 was above the 20th century average, but that still grouped it with the colder recent years - 2009, 2013, 2014. Then the March/April coldsnap dropped us below the 20th century average, and now the late-April heatwave has moved to just below the 20th century average again.

On a month-by-month basis this is how things have broken down:

Looking back at the past winter:

• December was warmer than the 20th century average, and it was about 1°C warmer than the recent 5-year average.
• January was also warmer than the 20th century average, but it was still about 1°C cooler than recent years.
• All the other months have been colder than both the 20th century average and the recent average.

So yeah, back in the 2017-2018 Winter in Review - Temperatures we saw that 2017-2018 wasn't that bad. But it's definitely been cooler than what we're used to.


Monthly Snowfall

Here we have the monthly snowfall at the International Airport, for both this winter and last winter.

This April we got 12cm of snow, most of which was during a big 10.4cm snowfall on April 16th. That's just a bit below average, and it's well below last year's record 43cm of snow in April 2017.

There's still about a 50/50 chance of snow in May, but so far this winter:

• September, October and March were well above average.
• December was well below average.
• November, January, February and April were all in the typical range.

Cumulative Snowfall

When we add the total snowfall up for the year right now we are at 116.9cm. That's below the 136.7cm from last winter, and below the Airport's average of about 125cm. But again, half of the time we'll get snow in May, with an average of 6cm.


Snowdepth

Here is our snowdepth for this winter:

• The International and Blatchford were both high in November
• They were both a little low in December and most of January
• At the end of January things took off, and we stayed pretty high through the end of March
• And then with our cold April the snow refused to melt. For a few weeks we were actually above any other recent years, even though this wasn't a particularly snowy year.

This winter the melt started in earnest on April 8th when the International was at 31cm of snow. By April 21st it had dropped to "trace" amounts, and then to 0cm by April 23rd. That put it ahead of 2013 and 2011 which first reached 0cm on April 27th and 29th respectively, but behind every other recent year.


May Temperatures

And finally, here is a quick preview of what temperatures might look like in May.

May hasn't had a High below freezing since 1959, so that's nice. But about one third of the time we'll have a few days that stay below 5°C. On the other side of things we should probably see a week or two of days above 20°C (2000 was the only real under-achiever, with 2 20°C days). 2015, 2016 and 2017 all had almost a week of 25°C days, and 2013, 2016 and 2017 each had a High of 30°C.

For Low temperatures, about a quarter of the time May will have no lows below 0°C, although more typically there are a a handful. If you are interested in when the final frost is likely to fall, we just looked at that last week.