There are very few comforts in Minnesota’s harsh winters. It’s cold, the snow makes accomplishing even basic tasks potentially deadly, and it lasts a looooong time.
But Minnesotans are an optimistic people, and you can always count on, on the bitterest of cold days, as the wind slices through even your hardiest winter gear, a well-meaning friend, colleague or stranger will offer cheerily, “Well, at least it’s too cold to snow!”
If only it were true.
In fact, it’s never too cold to snow. A review of 100 years of weather data (from the Minnesota DNR) shows that Minnesota has had snow on days when the temperature didn't get above -17°F — on January 16, 1994, it never got above 0, yet the Twin Cities were walloped with more than eight inches of snow.
So why does the idea of “too cold to snow“ persist?
Weather expert Kenny Blumenfeld, Senior Climatologist with the Minnesota DNR State Climatology Office, confirms that while it’s technically never too cold to snow, a few meteorological facts combine to make snow less likely on colder days:
- Physics of snowfall production. “The physics of snowfall production are optimized at temperatures below freezing but above zero (F). In terms of maximizing the amount of snowfall that you could get from a set amount of precipitation, the ‘sweet spot’ is basically in the teens. … If temperatures are outside of those ranges, you certainly can still get snow, but the processes are not nearly as efficient, and you get lesser accumulation rates.”
- Drier air. “Once you get to temperatures below zero, the air is naturally quite ‘dry,’ and it does not take much moisture to bring the relative humidity to 100%. Thus, even when you saturate the air at very cold temperatures, it still will not contain very much moisture. With scanty moisture and inefficient snowfall-production processes, you're not going to get much snow.”
- High pressure. “Perhaps the most common reason people claim this is that when it's very cold, we tend to have high pressure moving in. And high pressure means sinking air. Sinking air is hostile to precipitation processes (which require rising air). Moreover, the expanding pool of cold air tends to push the jet stream south, and the jet stream carries all of the interesting weather systems well to our south also. Those weather systems tend to have all the upward motions and whatnot required to produce precipitation and snowfall, so frequently if it's cold, it's not going to snow because the air is sinking and because the jet stream/storm track is so far away from us.”
So there tends to be less snow when it’s very cold, but “not because it is physically impossible to produce snow or because it's too cold for snow; it's because what's needed for snow is often lacking, by coincidence, when it's really cold,” Blumenfeld explains.
Indeed, snow accumulations do tend to decrease as the temperature heads south. In the chart below, each dot represents the high temperature and snowfall amount for each day in the past 100 years when the Twin Cities had more than trace amounts of snowfall. The really big snow accumulation numbers are found more in the teens to 32°F range; as temperatures drop below zero, snowfall totals are lower.
But it’s never too cold to snow.
Random Acts of Data is an occasional series by MinnPost news editor Tom Nehil. The goal: to answer questions about all things Minnesota using the vast amount of data at our disposal. If you have a question you’re wondering about, send an email to firstname.lastname@example.org with the subject line, “Random Acts of Data.”