versus - The Edmonton International Airport: Part 2

Today we're going to take another look at the temperatures at the Edmonton International Airport.

One of the earliest posts on this blog asked How cold is the Edmonton International Airport? But since then I've learned a bit, and I have a few new charts to play with, so I wanted to revisit it.

High Temperatures

Here we have a comparison of the daily High temperatures during the year for Blatchford and the Edmonton International Airport.

The colourful stuff in the background is the typical distribution of temperatures at Blatchford: the white line is the recent average for each day; it's surrounded by a grey area which is the 25th-75th percentiles where temperatures will fall about half of the time; and the oranges and blues are the recent highest and lowest temperatures. And then the Edmonton International's average, highest and lowest are shown in the darker blue.

When we compare the High temperatures for the International to Blatchford, we see that they're very similar. The average is a close match, although for February and March the International is about 1°C lower. The highest and lowest recent temperatures are also very close.

So for the High temperatures there isn't much to say, but that changes when we look at the Lows.

Low Temperatures

With the Low temperatures the International is consistently below Blatchford. Throughout the year the average Low is about 4°C colder at the International. And for some of the recent coldest days, many are 7°C or even 10°C below Blatchford.

To take a closer look at this, we'll break things into summer and winter.

Summer Lows

Here we have the Low temperatures during the summer. We won't bother looking at the Highs, because they're a pretty close match. But for the Lows, we can see that the International Airport is basically shifted down from Blatchford, by about 3°C colder. The the warmest and coldest Lows are shifted down too.

But how much colder should an airport be, compared to the city?

Calgary & Winnipeg Summer Lows

Here I've added the average temperatures for two Environment Canada stations in Calgary, and two in Winnipeg. Calgary is complicated, because it has no centrally located station - it's International is about 9km from downtown, and Springbank is about 22km away. Winnipeg does have a central station downtown at the Forks, and the Winnipeg International is about 8km from there. And in Edmonton, Blatchford is about 4km from the downtown, and the International is about 26km away.

So neither Calgary nor Winnipeg are a perfect comparison for the situation in Edmonton, but at least here we get to see how remote stations compare to more central ones.

For Calgary, the gap between the two stations is about 3°C, which is pretty similar to the gap for the Edmonton stations. The lines are squiggly and there's a lot of variability from day-to-day, but this is a reasonably good approximation of how the stations differ.

For Winnipeg we can see that the lines are quite a bit closer to one another. Eye-balling off of the chart there's about 1.5°C between Winnipeg stations during the summer, compared to 3°C for Edmonton and Calgary.

Winter Lows

Leaving summer behind, here we see how the Lows of Blatchford and the International compare during the winter months.

Again, the International's average is consistently lower - this time by about 4°C. And while the highest-lows at the airport are only a little bit below downtown's, for the lowest-lows there are some giant gaps, with the International dropping below -40°C or even -45°C while Blatchford was 8°C or 10°C warmer.



This chart ranks every low at the Edmonton International that was below 0°C, which works out to about 4,600 days over the last 22 years. The orange cloud is the corresponding temperatures at Blatchford on those days, and they can obviously vary a lot. For some days Blatchford is as cold as the International, or maybe even a bit colder, but for others it's much warmer.

With the trendline we can see that the gap between the stations generally increases the colder things get. For mild winter days there's about a 3°C difference, by the time we get to -20°C it's about 4°C, and below that things really drop off.

We'll take a closer look at those really cold days later on. But first, here are Calgary and Winnipeg again:

Calgary & Winnipeg Winter Lows

During the summer we saw about a 3°C gap between the Calgary stations, but during the winter they are much closer, with about 1°C difference between them.

For Winnipeg in the summer we'd seen that the Forks was a little bit warmer than the airport, by about 1.5°C. In the winter that opens up, with about a 3°C gap between the stations.

So Winnipeg and Calgary flip from summer to winter. In the summer the two Winnipeg stations are close, and in the winter they're further apart. For Calgary it's the opposite. And through it all Edmonton is comparatively consistent, with the International about 3~4°C colder for the whole year.

The coldest-Lows are interesting though. Winnipeg's average winter temperature is several degrees colder than either of the Edmonton stations, but we see don't that for it's extremely cold days (the dotted green line). And in fact, the coldest-Lows for the Edmonton International are often below those for the Winnipeg International.

The Really Cold Days

Normally I try not to go overboard with animation, but this chart could certainly be accused of that. Without the animation though, this would need to be many, many separate images, and today is already running long.

So this cycles through a whole bunch of stuff: Edmonton International vs. Edmonton Blatchford; Edmonton International vs. Calgary Springbank; Calgary Springbank vs. Calgary International; Calgary Springbank vs. Winnipeg International; Winnipeg International vs. Winnipeg Forks; and then finally Winnipeg International vs. Edmonton International. Through it all the Edmonton temperatures are shaded in the background for comparison.

This is trying to compare the coldest days since 2000 at each city's outlying stations, to the corresponding temperatures centrally. And the 200-coldest days in Edmonton aren't necessarily the same days as Calgary or Winnipeg.

With all of that information there are a few fun things to point out:

• On these very coldest days, Blatchford is always warmer than the International. The typical gap is 8°C (that's the mean, the median, and the mode). There was 1 day with only a 1°C gap, and 17 with 5°C or less. But at the other end there are 63 with a difference of at least 8°C, and 12 with a gap of 10°C or more.


• The line for Springbank's 200-coldest is a pretty nice match for the Edmonton International, except that the whole thing is shifted up by about 5°C. That places it a bit below Blatchford.


• The Calgary International bounces all over, which is probably because it's the least-central of these central stations, and therefore the least-moderated? For these very cold days it's typically 3°C warmer than Springbank (and again, that's the mean, the median, and the mode), but there are some days that are colder, and some that are much, much warmer.


• On these cold days the Forks is on-average 4°C warmer than the Winnipeg International. But of these 200 days, there are 45 days where the temperatures were the same. So the Winnipeg stations have a lot more in common with each other than the Edmonton ones do.


• The lines for the Edmonton International and Winnipeg International cross over each other, and Edmonton's 100-or-so coldest days are actually colder than Winnipeg's.

That last point is probably the most interesting one - the Edmonton International gets more really cold days than Winnipeg does. Throwing that into one more chart, we get this:

Since 2000, the Winnipeg International was the station here with the most days below -30°C, at 208 (174+31+3). But the Edmonton International had the most days below -35°C, and for days below -40°C it almost triples the Winnipeg International's numbers.

Since 2000, the coldest day at the Winnipeg International was -41.7°C, on February 5, 2007. And sure, that's cold. But in that same time-frame the Edmonton International had 9 days which were colder than that, including -46.1°C on December 13th, 2009. And that was actually the most recent time that the International has dropped below -40°C, with December 12, 13, and 14th dropping to -44.7°C, -46.1°C and -41.7°C respectively.

This winter, the coldest day was December 17 at -32.8°C (-27.3°C at Blatchford) which put it in 100th-coldest spot. For the winter of 2015-2016 the coldest was -29.3°C (-20.3°C at Blatchford) in 188th place. The winter of 2014-2015 reached 43rd spot with -35.8°C (-30.2°C at Blatchford). And if we go back 3 years to 2013-2014, that winter had a bunch of cold days: two at -39°C for 14th and 15th place, -38.3°C for 22nd, and so on,

On the other end of things, of these stations Edmonton Blatchford recorded the fewest lows below -30°C, while Calgary International had the fewest below -35°C.

(It is again worth mentioning that Calgary is being a little unfairly represented here, since it doesn't have a central station. Blatchford is half the distance of the Calgary International, and it's surrounded by city, but they're both big, empty airports. The Forks is very central, and it's also in a reasonably dense area (ie. not an airport). So it's tough to say where exactly Calgary would end up if it had a central station. It will also be interesting to see if the redevelopment of Blatchford will cause its temperatures to move even further away from the Edmonton International.)

Winter of 2016-2017

Finally for today, we're going to take a quick look at the temperatures for just the last few months:

This chart shows the Highs and the Lows for the International and Blatchford this winter. It starts with lines for the temperatures, with the Highs temperatures as dashed lines and the Lows below as solid lines.

Then it cycles through to highlight the difference between Blatchford and the International. Days where Blatchford was warmer than the International are filled-in in red, and we can see that that was pretty consistent for the whole winter. The gaps are bigger for the Lows, with the International dropping to -32°C four times this winter, while Blatchford was between -22°C to -27°C. But for the High temperatures there were also a few days during our big mid-February chinook when Blatchford was at 10°C or 15°C, while the International was 5°C cooler.

The days when the International had a warmer High or Low than Blatchford are also highlighted separately in blue, but those are pretty rare. Out of these 151 days, there were 2 days where the International's Low was about 2°C warmer than Blatchford's, and 3 where the High was 1°C warmer. There are a few other days where the International was warmer, but the difference was less than 1°C.

Summary

So that was a bit of a marathon, but now we have a definitive answer to "How cold is the International Airport" all in one spot:

• The High temperatures at Blatchford and the International are pretty close, but as we saw with the winter of 2016-2017, they're not a perfect match.


• The Lows at the International are on-average 3-4°C colder than Blatchford throughout the whole year, but for the very coldest days that gap increases to 8-10°C.


• The temperature difference between Edmonton and its airport is consistently more than for the outlying stations in Calgary and Winnipeg. And again, on the really cold days the difference in Edmonton is about twice as much as the other cities.


• And finally, we have vindication for Winnipeg! The Edmonton International is usually several degrees warmer than either of the Winnipeg stations throughout the winter, but its very coldest days are actually colder than Winnipeg's. So for about 6 days/winter that must make the Edmonton International one of the coldest major airports in North America (watch out, Anchorage) if not the world.

For me all of this just reinforces why temperatures from the International are not a great representation of what we actually see in the city. I said this the last time that we looked at the Edmonton International, and I'll say it again today: remember to plug your car in.