Sven Sundgaard: Why cold snaps can’t keep up with Minnesota's climate trends

It may or may not come as a surprise that this winter was pretty weak, despite two (almost) legit cold snaps.

Meteorological winter is now over. The 90-day period from December 1 through February 28 averaged just -0.2°F from the 1991–2020 normal. That was pretty much the story statewide.

Of course, winter temperatures are now 3 to 5 degrees warmer than just 50 years ago, so in that context, this winter was considerably warmer than a historic average winter.

The Twin Cities got as cold as -19°F, a figure that is actually within the realm of our (modern) average coldest winter temperature based on the 1991–2020 average. However, it falls short of the historic 1961–1990 average of -24°F and well short of the -27°F we could have counted on in the late 1800s. Meanwhile, International Falls didn’t even reach -40°F this winter, which was the historic average coldest winter temperature. This winter, they dipped only to -35°F.

Winter overnight temperatures are the fastest-warming of any period or season on a statewide basis. While average winter temperatures have warmed nearly 4 to 5 degrees over the past five decades, overnight temps have warmed by 7 degrees.

Another way to measure how pathetic this winter truly was is by looking at the ratio of record warm temps to record cold temps. Let’s compile, on a statewide basis, how many record high temperatures and record warm overnights there were compared to record cold overnight lows and record cold daytime highs this winter.

Despite seeming “cold” (truly, only someone born in the late 1990s or later would consider this winter cold because they lack historical context), there were 197 WARM records broken compared to 110 COLD records broken, a ratio of nearly 2:1. Also compiled in the table above are each of the last 10 winters. You can see that last year was absolutely OFF THE CHARTS warm, with a warm-to-cold record ratio of nearly 155:1. Overall, record warmth outpaces record cold by a MORE THAN a 2:1 margin statewide.

Let’s look at this winter more specifically.

When we chart out each day in terms of its temperature anomaly (or departure from the 1991–2020 average), we can see the ups and downs of this meteorological winter. I’ve also highlighted some of the more significant time frames so you can see how many warm (red) or cold (blue) records were set across Minnesota.

As expected, in keeping with all recent trends, the “warms” are consistently warmer than the “colds” are cold.

To be sure, the mid-February cold snap was the most significant. Despite temperatures being overall warmer than the mid-January cold snap, it was the time of year that broke records. It was unusually late in the season to see what was essentially a January air mass.

I talked about the likely culprit of the unusually cold air, which pushed unusually far south for mid-February, in a recent article. To summarize, the Arctic saw its lowest amount of sea ice on record in February. Open ocean water releases a lot of heat and absorbs much more sunlight than ice-covered seas. This helped lead to record warmth deep into two main areas of the Arctic, splitting the polar vortex into two lobes and pushing it farther south.

Case in point: While we broke 77 cold records in February compared to 12 warm records in Minnesota, Alaska broke 61 warm records and only 2 cold records. On average, in February, the Alaska region was +3.3°F above normal, compared to the central U.S. (including Minnesota and the Northern Plains, which were cold), which was just -0.2°F below normal.

So yes, we had a couple of bouts of legit cold air this winter in Minnesota, but they don’t compare to historical cold air masses because the Arctic was yet again well above any historic or modern averages. Warmth, yet again, outweighed cold—both here and across the Northern Hemisphere.