Behold, the January Thaw!

It's a scene familiar to most Minnesotans: after a period of deep cold during January, we experience a run of mild conditions, often pushing temperatures above freezing. Indeed, the famed "January Thaw" is a common creature of Minnesota's winter, especially in western and southern parts of the state.

A January Thaw is defined as two or more consecutive days with maximum temperatures above 32 degrees F. These thaw episodes are a regular part of Minnesota's climate, bringing a brief respite to a Minnesota winter. January Thaws are most common and often most dramatic in southwestern Minnesota, where the local topography can boost daytime temperatures above freezing with relative ease, and sometimes even above 60 F.  Although less extreme, January Thaws also occur most years throughout southern and western Minnesota.

In the Twin Cities, January Thaws occur 94% of the time. For comparison, a "White Christmas" in the Twin Cities (one inch or more of snow cover on Christmas Day) occurs about 72% of the time, meaning we are more likely to have a January Thaw than a White Christmas, and this is true in all but the northern third or so of the state.

With at least one January Thaw now recorded in 2022, the streak is currently 11 years and counting; the last winter without a January Thaw in the Twin Cities was 2011.

The longest January Thaw on record in the Twin Cites is 18 days, spanning January 13th through 30th of 1944. That run of warm weather included a reading of 58 degrees F on the 25th, which still stands as the warmest January day on record in Minneapolis.

January Thaws exhibit some interesting long-term behavior, especially given the unmistakable trends in recent winters. For instance, January is Minnesota's fastest-warming month, with temperatures across the state increasing by 8-10 degrees F between 1970 and 2021. Yet the frequency of January Thaw events remains largely unchanged, and the length of these events shows no sign of increasing.

For instance, of the seven thaw events lasting 10 days or more in the Twin Cities, only one, in 1981, occurred during the period of modern winter warming, and each of the other six occurred prior to the end of World War II! This suggests that winter's dramatic warming trend is taking place without dramatically increasing the number of January Thaw days. The relationship between relatively cold and relatively warm days has not changed appreciably. What has changed, is the average temperature on any day. Cold days and warm days alike are now generally warmer, and often much warmer, than they had been historically.

Longest January Thaws on Record in the Twin Cities