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 northern and eastern Minnesota.

In the Twin Cities, January Thaws have occurred 82% of the time historically (back to 1873). 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 one January Thaw now recorded in 2024, the streak is currently 13 years and counting; the last winter without a January Thaw in the Twin Cities was 2011.

Given that some January Thaw events begin in December or end in February, we include these overlapping events when ranking thaw length, as long as the run of consecutive days includes at least two days in January. The longest thaw on record occurred is 24 days, from January 22 through February 14, 2024. The next longest thaw is 21 days, from December 19, 2006 through January 8, 2007. For thaws contained entirely within January, the longest on record 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 single 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 7-10 degrees F between 1970 and 2024. Yet the frequency of January Thaw events remains largely unchanged, and the length of these events shows no sign of increasing.

As an example, of the 17 thaw events lasting nine days or more in the Twin Cities, only four occurred during the period of modern winter warming since 1970, and 12 of the remaining 13 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