The number of days per year, in 20 year statistical averages, that MSP Airport has dropped to the teens below zero or colder
(FOX 9) - Coming off the heels of another Minnesota winter, it’s tough to even think about how our cold just isn’t what it used to be. But it’s true. Temperatures just don’t dip as far below zero as they used to, which I’m sure many of us are okay with.
Since 1900, the Twin Cities has certainly seen ups and downs in both temperature and precipitation. Year-to-year, decade-to-decade, and even century-to-century variability is perfectly normal as North America, and Earth as a whole, go through cycles. Our latest is certainly our trend to warmer temperatures, especially overnight lows.
A chart showing the number of days per year that temperatures dipped to -10° or colder in the Twin Cities. The green line indicates the rolling statistical average for the metro. The number of days has really declined in the last 30 or so years.
Through much of the 20th century, it was commonplace for temperatures to dip to or below 10 degress below zero many times during the winter. For the first couple of decades, the Twin Cities averaged 13 days per season with temperatures getting to 10 degrees below or colder.
But with a couple of very cold decades in the 60s and 70s, temperatures dipped to the teens below zero 16 times a season on average. That’s why many in the baby boomer generation remember temperatures getting so much colder when they were kids or in college… because they did! Since the 80s, however, these extremely cold temperatures have become far less common. These temperatures have gone from an average of 16 times a season to just 5 since the year 2000. This season, it has just happened twice.
So now comes the question of "why?". There are likely a number of factors involved, from climate change to the urban heat island to the way we actually calculate temperature (switching from human to automated observations). So how do we know what’s causing it? Well, we don’t. But, one way we might be able to narrow it down would be to compare other climate sites to the metro. If we compare the Twin Cities to St Cloud, you can see some differences.
The number of days per year, in 20 year statistical averages, that St Cloud has dropped to the teens below zero or colder
St Cloud is inherently colder than the Twin Cities because of its location further northwest. So the city should be a little colder than the metro on average. Therefore, you have to focus more on the overall increase or decrease in the number of times the temperature has reached 10 degrees below or colder.
Just like the Twin Cities, St Cloud experienced a pretty steady number of these cold days through 1960. Then came the couple of cold decades. But starting in 1980, the amount of teens below zero really started dropping, but not as much as the metro. The amount of days spent below minus 10 degrees dropped roughly 40% in St Cloud from 1960 to 2020. In the Twin Cities though, that number has dropped nearly 70%.
With such a drastic difference in the drop in the bitterly cold days, I’d say it’s safe to assume that the urban heat island in the Twin Cities is playing a role in our warmer nights. But how much of a role? Is that what is causing St Cloud’s drop too? Or is it climate change? How much of a role does year-to-year and decade-to-decade variability play? All of these are good questions and we have firm answers to none of them. That’s what makes statistical climatology so complex. Whatever the reason, we are certainly experiencing fewer of these wicked cold days and, for the moment, that shows no signs of stopping.