136 Years of Winter Patio Weather

Lets assume that "winter" runs from November through February. That's 120 days.
(March is a tricky month - usually quite nice, but occasionally not - so for today I'm going to leave it out.)

Of the 120 days of winter about 50 will typically be above freezing, although there is a lot of variation. In 1955 there were only 14 days above freezing, while in 1976 there were 78. Closer to home in 2011 there were 70, or well over half the winter. That's not so bad.

(and for anyone who thinks I'm cheating by leaving March out, it averages an extra 20 days above freezing, which would move the average to 70 days out of 150)

From the chart it looks like the trend is an overall increase, with an additional 2.1 days for each passing century. But unfortunately I'm not sure that there is actually enough data here to properly fit a trendline, because if I remove 1880-1890 then the line flattens, and it actually shows a slight decrease (-0.04 days per century). The limited data available might be too variable to draw that type of conclusion.

Instead of trying to find a trend, lets look at some discrete time periods. Jumping back 100 years, how did the end of the 19th century compare with the dawn of the 21st?

Here we also see a 2 day per century increase, so maybe that initial trendline isn't too far off?

Choosing to go back 100 years is pretty arbitrary though, so instead here are the 10-year periods with the most and the least days above freezing.

Personally, I find it completely amazing that 1898-1907 had more warm winter days than today.

The coldest 10-year period 1964-1973 includes the infamous winter of 1968-1969, which had a 26 day stretch where the temperature was never above -21°C. And just generally the 40's through 60's had fewer warm days than the rest of the century.

There's a strange situation, where if you were born in the 1940's through the early 1970's, and you think "It never got this warm when I was a kid", then you are right - in a modern winter there are about 10 or 15 more days above freezing. But if you were born in 1885 through 1920, your childhood winters would have had about as many warm days as today.

Now admittedly, 0°C isn't exactly patio weather. But I like using it as a baseline because in the middle of winter any day above freezing is pretty nice. And as we've previously seen, a little under half of our winter days will actually be above zero.

As for genuine patio weather, most trips will need to have some form of thermal assistance, because not even a handful of days each winter reach above 10°C. But it's surprising to see that if you are searching for winter patio weather, your best bet might be head back a century. There were 30 solid years with more days above 10°C than we are used to today. The older weather data is a little less precise than the current stuff, and so that might lead to a few extra outliers, but February of 1896 would still have been a nice enough time to head to Whyte Ave.

This also shatters one of my personal myths - I would swear that when I was a kid it was not this warm, and that we didn't have so many false "springs" each winter. But in fact I am wrong, because my childhood decade actually had a few more warm days than we have been seeing recently. I'll use the excuse that I grew up in the chilly suburbs, but the truth is that I was probably just underdressed.

Even though the numbers over the last century are surprisingly consistent, I never want to give the impression that this blog is climate change denial in disguise. I chose to look at the history of "warm" winter days first because I thought the results were genuinely surprising. Anecdotally, I think that most Edmontonians would have expected a much more significant increase. Yes, it is up since the 70's, but even in the last 30 years things have been fairly steady.

Warm days are only part of the picture though, so I'll end off with average temperatures.

Even though Edmonton's warm winter days have been surprisingly consistent since the 1880s, the mean daily temperature has been steadily increasing. And if the warm days have stayed basically the same, then that means the cold days must really be changing. But we'll leave that for another time.