Record Watch - April 18 & 19

Earlier this week I was insisting that we get warm weather like this all the time in April, and then we go and break a record which obviously doesn't happen everyday. But the point still stands - warm days in April aren't uncommon - and we'll look at that a little bit more. But first, the record:

On Monday April 18th we hit 25.5°C, breaking the old record of 25°C that was set in 1910. Runners-up were 23.3°C in 1891, 23.9°C in 1923, 23.3°C in 1926. and more recently 22.8°C in 2010.

We also broke the record for the daytime low at 9.3°C, well above the 6.9°C set in 1990.

So on Monday we set some records, and the forecast for Tuesday April 19th had been calling for as high as 27°C, but we didn't get there:

23.8°C on April 19th puts us in third place, after 24.5°C in 1980 and 25°C recorded in 1943. And as I'm typing this the overnight low hasn't been recorded yet, but the previous record was 9°C set in 2010.

There is a bit of a problem with weather records, in that the record for one particular date on the calendar doesn't have any connection to the records on either side of it. So you can get very different records, just by moving a day or two. As an example, lets look at the two records that we set this winter:

The two records this year were February 9th with a high of 10.1°C, and February 26th at 15.3°C. Those were the warmest temperatures recorded on those dates going all the way back to 1881, which sounds really impressive. Except that the record for Feburary 8th is 13.9°C (set in 1954) which is almost 4°C higher than the one we set for the 9th, and the February 27th record of 16.7°C (set in 1889) is 1.5°C above than the new record for the 26th. So just by moving one day either way you can end up with very different temperature records. It's something to keep in mind whenever the subject of temperature records comes up.

The same thing is true for this part of April. The records for this week are:

• April 15: 26.9°C set in 1984 
• April 16: 28.1°C set in 1984
• April 17: 26.7°C set in 1923
• April 18: 25.5°C set in 2016
• April 19: 25°C set in 1943
• April 20: 26.7°C set in 1934
• April 21: 26.7°C set in 1942

So while we set a record this year, it's a bit of an underachiever compared to its neighbours.

To give a little bit more context to recent history, here are some of the warmest temperatures for the whole third week of April, going back to 1985:

The white&grey columns just break things up by year, and you can see that warm days often clump together. So we had a warm week this year, and last year, and 2010, and 2005, and so on. There was also a noticeable drought of warm days from 2011-2014. On the list of the top 50 days, 2016 claims the #1, #4, #13 and #42 spots.

Going back to my original claim that 20°C days in April aren't all that unusual, here is the list for the entire month of April, again going back to 1985:

Since 1985 Edmonton has had 70 days above 20°C in April, or a little over 2 per year on average. But they do clump together, so some years have more than others. Most years are represented, but the ones that are missing are 1985, 1993, 1995, 2002, 2007, 2011 and 2012. And then there are the warm Aprils that really stand out, like 1998, 1992, 2010 and 2015.

And just one final note - the highest temperatures ever recorded in April were 31.1°C on April 29th 1939, and 30.1°C and 30.3°C on April 25th and 26th 1977.