versus: Calgary - Part 1

In previous posts I've looked at how Edmonton's weather compares to the International Airport, and to some nearby rural stations. But today it's time for the main event - the battle of Alberta - Edmonton versus Calgary.

Beyond just perpetuating civic rivalries, I am actually curious how different the two cities are. And occasionally if I see something strange in the Edmonton numbers it would be nice to have another reference to compare it to.

This will be the first part of the Calgary comparison, looking at recent~ish temperatures going back to 1995. These should be reasonably representative of what we would see in a typical year.

Here is my standard rollercoaster chart showing how Edmonton's temperature varies throughout the year:

The white line is the average, the grey band is the 25th-75th percentile range, and the oranges and blues are the warm and cold extremes.

Here is the same chart of Edmonton's highs, but with the temperatures for the Calgary International Airport overlaid in red:

We can see that in the summer the high temperatures for the two cities are very close, but in the winter Calgary's average high is warmer.

Here are Edmonton's lows, compared to Calgary's in red:

And we can see that the winter lows are actually quite close, but in the summer Calgary's lows are a little bit cooler than Edmonton's.

Here is a closer look at the winter months, and I've also added the highest and lowest temperatures for Calgary to give a better sense of the fluctuations.

In the deepest, darkest depths of winter, Calgary's highs are 3-4°C warmer than Edmonton. It surprises me that it is that consistent, although thinking about it I guess that there are plenty of times when Edmonton is -10°C with Calgary at -6°C and I wouldn't even give it much thought.

That 3-4°C swing is right around the freezing mark, and it means that Edmonton's average high is below freezing from early-November through mid-March, while Calgary's average is only below freezing from late-November through early March. Those are just averages, and Edmonton will certainly have days above freezing during that period, but that small difference in degrees and that extra month-and-a-bit with melting might explain where all of Calgary's snow goes.

For the range of the highs, we see Calgary's famous chinooks with the highest highs being several degrees above Edmonton's. The lowest highs are very similar to Edmonton's.

The winter lows for the two cities are also very similar, with Calgary being maybe a degree warmer on average. The range from highest to lowest is also very similar, although in the last 20 years Calgary has gotten closer to -40°C than Edmonton has. So Calgary will get warmer than Edmonton during the day, but just about as cold at night.

For the summer we see the opposite story.

The two cities have very similar high temperatures, with very similar ranges. Edmonton does seem to be a little bit warmer in June, with Calgary a little bit warmer in August.

For the average overnight lows though, Edmonton is consistently several degrees warmer than Calgary during the summer. The average lows for Calgary are right inline with the 25th percentile for Edmonton, and the whole range of Calgary's lows is shifted down from Edmonton's. Looking at the period where Edmonton's average low is above freezing, it's about 3 weeks longer than for Calgary. These are just averages so they won't be a perfect match frost-free days, but it's the same basic idea.

Here's a closer look at the melty and frosty periods for Edmonton and Calgary:

I'm just eye-balling these off the graphs, and since they are averages they don't really correspond to anything - any given year will bounce around a lot more. But a few degrees difference right around the freezing mark means a few extra weeks of melts or frosts for the two cities.

One thing to note through all of this is that I am comparing data for Edmonton Blatchford (the former City Centre Airport) to the Calgary International Airport. Unfortunately, Environment Canada doesn't have a "downtown" weather station for Calgary, so this is the best comparison that I can make.

To give a sense of how things do vary, here are the high temperatures for Blatchford and the Calgary International, as well as for the Edmonton International, Canada Olympic Park, and the Springbank airport outside of Calgary:

For the high temperatures we see that the Calgary stations are grouped together, and the Edmonton stations are grouped together.

For the lows there is a little bit more variation:

The Edmonton International does get quite a bit colder in the winter than all of the others, and COP has the highest-low temperatures in the winter (as a non-Calgarian that seems strange to me. But I checked the numbers and they seem to be correct?). In the summer all of the stations are below Blatchford, with Springbank's average sitting around Blatchford's lowest.

In terms of distances, Blatchford is 4km from downtown, the Calgary International is 9km, COP is 10km, Springbank is 22km, and the Edmonton International is 26km.

So with the data that's available I think that a comparison between Blatchford and the Calgary International makes reasonable sense. But for a margin-of-error due to not having a downtown Calgary datasource, this gives some idea of the variation. For Part 2 of this Versus match I'll be looking at trends going back to the 1880s, and for that the only two stations available are Blatchford and the Calgary International.

With all of that said then, it looks like Calgary really does get warmer winter days than Edmonton, although they can't gloat too much because they get basically the same cold nights that we do. And as one of my Calgary friends used to say, Edmonton's warm summer nights make sitting on a patio here more pleasant. This is all based on averages which aren't my favourite things, so in Part 2 I'll try to put this into a bit more context in a few weeks.