December 22-31, 2023

After several weeks of widespread anomalous warmth across the Midwest, the last week of December proved to be no different. In fact, average temperature anomalies were at their highest during this final week of the month. Most of the Upper Midwest observed average temperatures over 15°F above normal (Figure 1). Much of Minnesota and Wisconsin saw average temperatures 20-25°F above normal. Statewide average temperature anomalies ranged from 8.5°F above normal in Kentucky and 10.6°F above normal in Missouri, to as much as 20.9°F above normal in Minnesota.

Minimum temperatures were even more anomalous. Minimum temperatures were 15-20°F above normal across the Midwest (Figure 2). For many locations across the Upper Midwest, normal minimum temperatures in late December should be near 0°F. In International Falls, Minnesota, a minimum temperature of 34°F was 34°F above normal and the warmest on record. Des Moines, Iowa recorded a minimum temperature of 46°F, which was 28°F above normal and the warmest on record for December 22.

By December 23, stations across the Midwest were seeing minimum temperatures over 20°F above normal, and records were being broken. On Christmas Eve, minimum temperature records were set in the Twin Cities; St. Cloud, Minnesota; Duluth, Minnesota; International Falls; Eau Claire, Wisconsin; Milwaukee, Wisconsin; Madison, Wisconsin, and several more locations across the region. This continued on Christmas Day, with a record warm minimum temperature of 50°F set in Chicago. Records continued to be broken in the days after Christmas, although with more isolated areas of anomalous warmth. By December 28, new minimum temperature records were confined mostly to Michigan. Alpena, Ann Arbor, Flint, Saginaw, and Ypsilanti all recorded minimum temperatures of 20°F+ above normal.

The warmth was seen in maximum temperatures too. In Michigan, Minnesota, and Wisconsin maximum temperatures were generally 10-15°F above normal, while in the rest of the region they were generally 5-10°F above normal (Figure 3). The period was off to a warm start in Red Lake Falls, Minnesota, where a record high of 53°F on December 22 was 34°F above normal and the warmest on record. This was not far from Beltrami County, Minnesota, where abnormally warm conditions caused the melting of local lake ice cover, inducing a rescue of 122 anglers from a broken ice floe. It was common during the final week of the month to see temperatures reach 30°F above normal, especially since normal maximum temperatures in the Upper Midwest are generally below the freezing mark.

By Christmas Eve, southern parts of the region were reaching near 70°F. A temperature of 67°F in Washington, Indiana on December 24 was the warmest on record in over 125 years of recordkeeping. After Christmas, there was still some anomalous warmth. Temperatures reached the upper 40s and 50s—over 20°F above normal—in Wisconsin on December 26, with records broken in Madison, Wausau, and Eau Claire. The National Weather Service in Des Moines, Iowa reported daffodils sprouting as late as December 29. Even when temperatures did fall toward the end of the week, above-normal temperatures continued across the Upper Midwest, while temperatures fell to near or below normal across Missouri, Illinois, and southern Indiana (Figure 4).

More Precipitation To End the Month

December’s final days ended with more precipitation than previous weeks across the region. Much of Minnesota and Missouri received nearly 2 inches of rain, while the rest of the region saw generally 1 inch or less (Figure 5). This culminated in some monthly precipitation records, including St. Cloud, where 3.35 inches of rain was a record for the month of December in over 100 years of recordkeeping. In fact, 2.43 inches of that rain fell during the final week of the month. A system that came through the region during the Christmas holiday (Figure 6) brought mostly rain, even in the Upper Midwest, although parts of western Minnesota did see some frozen precipitation. As this system meandered over the middle of the country, it continued to drop much needed precipitation, with parts of northern Minnesota running 2-3 inches above normal for precipitation.

As the upper-level low spiraled across the middle of the country, several bands of snow set up on the back end of the system where cold air was being drawn in. The heaviest snow was along I-80 through Iowa, as well as along the Mississippi River through the Iowa/Illinois border. Just about 2 inches of snow fell between Davenport and Dubuque, with generally 1 inch along I-80 in the days following Christmas (Figure 7).

Drought Persists

Yet again, there were no improvements through the end of the year. The Drought Monitor was updated on December 26, and at that point, while some precipitation had fallen across the western Midwest, it was not enough to make a dent in dry conditions. Wisconsin and Minnesota received some above normal precipitation through Christmas, but with significant improvements already made during the Fall, it was not enough precipitation to warrant further drought removal. D0-D2 conditions remained through much of Minnesota and Wisconsin (Figure 8). Similar conditions have been noted in Indiana, southern Illinois, and much of Missouri, where precipitation did not make much of a dent pre-Christmas.

There were no improvements through the end of the year. Slight degradations were made across the region, with a 3% increase in D1 (moderate drought) coverage through January 2. There was not enough precipitation after Christmas to provide much drought relief anywhere. D4 (extreme drought) remained through the end of the year in Iowa, where it covered 35% of the state as of the new year.