There has been a fair bit of talk and media coverage on the cold weather we, and much of central and eastern North America, have seen so far this winter. For this issue I thought I would dig into the weather data and try to see just how cold we have been.
First of all, I don’t think anyone can argue this hasn’t been a cold winter. As we all know, December 2013 was the second coldest on record, with average monthly temperatures running 5 to 7 C below the long-term average. That said, while we did see some really cold days, very few cold records were set during the month. What made the month so cold was that we never really got a break from it!
There are a number of different ways we can compare temperatures to try and determine just how cold it was. One way is to compare just how far we were below average compared to other places on Earth during December. I came across a report that the University of Alabama in Huntsville puts out, that discusses global temperatures and their departure from average. In the report they point out which places or place on Earth had the warmest and coldest temperatures in regard to how much they departed from the long-term average. During December, the coolest area globally turned out to be in central Manitoba, near Lake Winnipeg, where temperatures in the troposphere (the lower part of the atmosphere) were 5.37 C (about 9.7 F) cooler than the long-term average. So, I guess we could argue that we were the coldest place on Earth during December! I then looked at January’s results and found that the coldest region on Earth shifted a little southeastward and was now centred over far-northern Michigan, covering a larger area made up of most of the eastern U.S. and Canada, stretching from just south of Hudson Bay through to the Gulf of Mexico.
The University of Alabama in Huntsville also produces a global map of the monthly temperature anomalies. I have included January’s map here, and if you take a look, you can easily see just how far below average our part of the world is. You can also see that, besides our region, very little of the world saw colder-than-average conditions. Now, before we start crying “Not fair,” we need to remember: eventually this weather pattern that’s giving us these cold conditions will change, and as you can see on the map, we’ll likely switch to a warmer-than-average pattern, given the fact that most of the planet is seeing warmer-than-average temperatures. Also, when you think about it, I think I’d rather have colder-than-average temperatures in the winter, when it’s going to be cold anyway, rather than experiencing them in late spring or summer.
More from the Manitoba Co-operator website: Warm, cold and the polar vortex
OK, now back to looking at the two-month cold snap we are experiencing and how we can determine just how cold it is. I guess the tried-and-true method is to simply go back into the long-term weather records and compare this winter’s temperatures to that of previous winters. I used Winnipeg’s data for this as it has the longest period of record, and when we have cold weather, it tends to affect all regions of southern and central Manitoba. The first thing I looked at was the number of times we’ve seen mean monthly temperatures colder than -20 C. It turns out there have been 80 months going back to 1872 that have been colder than -20 C. When we compare December 2013’s mean monthly temperature of -20.9 C to these months, I found that it falls into 65th place, which means that we’ve seen 64 colder winter months. The most recent cold month was January 2004, which had a mean monthly temperature of -21.7 C. The coldest month ever recorded in Winnipeg was in 1875, when the monthly temperature for January was a frigid -27 C. The second coldest was in January 1966, with a mean temperature of -26.7 C. So, when we look at it from this perspective, December 2013 was not really that cold.
How about if we combine December and January and see how they compare to other years? As it turns out, we don’t see two or more months in a row with really cold temperatures that often. I only counted 11 times in 142 years of data that had both December and January reporting well-below-average temperatures. The last time we had a really cold December-January period was in the winter of 1978-79, when the mean temperature was -20.1 C. This compares to our mean temperature for this winter of -19.9 C. The coldest December-January was in 1886-87, with a mean temperature of -23.1 C. The coldest modern-day winter was in 1949-50 where, thanks to a very cold January, the mean temperature for the December-January period was -21.1 C.
If our cold weather continues to the end of February, then it will truly be a cold winter! Looking back, I could only find three winters (December to February) that had all three months reporting below-average temperatures. You have to go all the way back to the winter of 1916-17, when the mean temperature for those three months was -20.1 C. We would have to see this February’s mean monthly temperature come in at -20.4 C to tie this, and with a mean temperature of -21 C over the first eight days, I guess it might be possible. The coldest winter ever recorded was in 1886-87, with a mean temperature of -22.9 C. We would have to have a mean February temperature of -29 C to tie this record, so I think it’s safe to say that this will not be the coldest winter ever.