SOME COLD TRUTH

International Falls, the so called the 'Ice Box of the Nation,' broke a record low temperature for the date of February 3rd (not an overall record, but just for that date specifically). That's some legit cold, but what's it really mean in the scheme of things?

The coldest ever recorded in International Falls is -55° set in 1909, more than a century ago. While -40° is definitely cold, especially to those of us in southern Minnesota, International Falls actually hits this temperature with some regularity, even in the last two decades. In fact, the average coldest winter temperature is between -37° and -41°. This is the range you get when you look for every 0.5 to 1.4 years in the data. They hit -42° last February as well.

Let's dive deeper into the data because there are some interesting trends. International Falls, like basically everywhere in Minnesota is warming of course, but all warming isn't equal.

Above is a temperature plot of average winter temperatures (highs & lows for Dec, Jan, Feb) from 1970 through 2021. The trend is pretty dramatic. International Falls average winter temperatures have warmed +5.8° F in just 51 years.

For comparison, the Twin Cities is warming at +5.6° F in 51 years.

And for yet another comparison, with Duluth, also in the northern half of the state (& with a long record like the Twin Cities): very similar at almost +6° F warming.

BUT, when we look at the extremes: the coldest temperature of the winter season, we see something a little different. International Falls coldest temp of the season is warming at half the rate of the average temperature: +2.7° F.

What does this mean?

Well, International Falls is still the beneficiary of some of the coldest air the northern hemisphere can muster. If you pay attention regularly, they get many more 'swipes' if you will, of the arctic air than we do in southern Minnesota, even just 250 miles south. Indeed our planet can still produce some very cold temperatures in the depths of winter because even in a warmer world, there's still NO sunlight above the arctic circle in our winter (or antarctic circle in their winter). That means ground & air still cool for three months, just not quite as much as it used to, but it's not hard to produce at least a small pocket of very cold air, on the order of historic proportions, just not as much as there used to be. That's why the average temperatures are much warmer but you can still get an extreme now & then.

In case you're curious, I produced a map showing the normal coldest temperature of winter for select locations around Minnesota and western Wisconsin. These are 2020-2022 averages, so modern averages. Historically of course these would be 2° to 6° colder, except in the Twin Cities it's even more dramatic at about 11° colder because of our urban heat island exacerbating the warming.

You can see MSP sticks out and you can easily derive that if not for all our urban sprawl we'd probably see an average coldest temperature in winter of also about -20°, which funny enough, the magnitude of the urban heat island on clear, cool nights is about 4°.