Late-March Heatwaves

The forecasts for this week are looking pretty warm, so today we are looking back at some historically warm March days.


50 Warmest Days: March 18-24

This chart has the 50 warmest temperatures for the 2nd last week of March - the 18th through 24th.

The warmest records for this week are March 22nd and 23rd at 21.1°C and 22.2°C respectively, both set way back in 1889. The coldest record is almost 10°C lower, with the 24th way down at 13.6°C set in 2004. The records for the rest of the week are all between 17.2°C and 19.4°C.

In terms of decades the 1910s have 13 entries in this Top-50, across 4 years: 1910, 1911, 1912 & 1915. And the 1880s have 9, across 1884, 1885 & 1889. In comparison the 2000s only have 1 entry, with March 24th's 13.6°C record.

The cutoff to get into this Top-50 is 12.2°C, and so at the end of the week we will need to see if 2019 has added any entries.


50 Warmest Days: March 25-31

Moving on to the last week of March - the 25th through 31st - things change a little bit.

For this week the records range from 15.1°C for the 27th and 15.6°C for the 25th up to 21.1°C for the 31st and 23.5°C for the 30th. And here the cutoff for the Top-50 is 13.9°C, compared to 12.2°C for the week before.

The 2010s are much better represented here, with 7 entries across 2010, 2015 & 2016. And the 1990s have the most entries with 8, across 1990, 1991, 1992, 1994, 1995 & 1998.


Records

This upper line on this chart shows how much the records for the back-half of March vary. Most of them fall between 15°C-20°C, but there are a few outliers up above 20°C and below 15°C.


Recent Marches

In recent years 2004 was the only March with a day which hit 20°C, and 2004 & 2015 both had days hit 15°C. So those were the only particularly "hot" recent Marches.

Below that most Marches have had at least one day which hits 10°C. The recent exceptions being 2018, 2011, 2006 & 2002. And we've already had one of those in 2019.


The Big Melt

Last week was fairly warm, and here we see the effect it has already had at the snowdepth at the International Airport. The airport peaked this winter at 45cm on March 10, but dropped to 35cm by the 16th. Last winter late-March and early-April were both very cold, so the big melt in 2017-2018 didn't start until mid-April.

Here's one more look at how snowdepth changes over the course of March & April.

This year we started March well above average at 37cm, and in Mid-March we're still well above average. But by April 1st many previous years have melted down to 0cm or near 0cm. The forecast for the rest of March is looking fairly warm, so we will have to see where we end up in a few weeks.


Updated for 2019:

So in the end, the week of March 18-24 ended up with 5 Highs in the Top-50. And those are the only entries in the Top-50 for the 2010s.

Those 5 days all set warmest-since-1996 temperatures, but they were still a few degrees below the warmest-since-1880 records.

And the warm week made a dent in our snowdepth, with Blatchford dropping down to 1cm, and the International falling to around 20cm.