December 2023 Overview – Midwestern Regional Climate Center

Temperature

The average December temperature for the Midwest was 36.8°F, which was 9.1°F above the 1991-2020 normal. The Midwest had the second warmest December since 1895. Unusual and persistent warmth blanketed the region with temperatures 2-6 °F above normal across the lower Midwest and 7-15°F above normal across the upper Midwest (Figure 1). Statewide average temperatures ranged from 4.5°F in Kentucky to 13.5°F above normal in Minnesota. Minnesota shattered the previous record warm December, which occurred in 2015, by 4.9°F. Other notable statewide warm temperature ranks include Wisconsin (1st), Iowa (1st), Michigan (2nd), Indiana (3rd), Illinois (3rd), Ohio (3rd), and Missouri (3rd). Nearly all of the long-running weather stations across the upper Midwest had record warm or near-record warm (top 5) monthly average temperatures for December (Figure 2). Over a dozen Midwest locations had a record mild start to winter according to the MRCC’s Accumulated Winter Season Severity Index (AWSSI) (Figure 3). Milwaukee tied the record for the greatest number of days at or above 50°F in December, with 8 days. On December 14, International Falls, Minnesota, reached a high temperature of 52 °F, which was their 3rd warmest December temperature since records began in 1895. The persistent warmth led to unsafe ice conditions, cancelled dog sled races, and even early sprouting of trees and flowers.

Precipitation

December precipitation totaled 2.19 inches for the Midwest, which was exactly normal. Precipitation was variable across the region, though, with conditions generally transitioning from wet in the northwest to dry in the southeast (Figure 4). Locations throughout Minnesota were 1-3 inches above normal. Above-normal precipitation was also observed along an axis from Kansas City, Missouri to Chicago, Illinois. Conversely, across the far southern Midwest and Ohio River Valley, precipitation was about 1-3 inches below normal. Statewide precipitation totals ranged from 1.79 inches below normal in Kentucky to 1.06 inches above normal in Minnesota. Minnesota tied the wettest December since 1895, matching the previous record (set in 1968). St. Cloud, Minnesota had the wettest December in 123 years of record keeping with 3.35 inches.

Snowfall

December snowfall was minimal and deficits were widespread as persistent warmth drove precipitation to fall more as rain instead of snow. Snowfall totaled 0.5-15 inches across the upper Midwest (Figure 5), which was about 2-25 percent of normal (Figure 6). The Great Lakes were nearly ice-free in December, which is generally favorable for lake effect snow. However, the lack of cold arctic air crossing the Lakes meant lake effect snow was suppressed regionwide. As a result, snowfall in Michigan’s Upper Peninsula was 10-40 inches below normal for the month (Figure 7). The December snow drought resulted in little to no snowpack across region. By late December, most of Minnesota, Wisconsin, and northern Michigan should have persistent snowpack on the ground that is about 5-24 inches deep, but instead these areas ended the month with mostly bare ground. Further south, snowfall totaled 0-5 inches across the lower Midwest for December, which was 0-50 percent of normal for most areas. Indianapolis recorded their first measurable snowfall of the season on December 31, which was the 2nd latest on record (dating back to the 1884).

Drought

Drought persisted during December with some areas showing modest improvements and others having modest declines. Overall, the month ended with about 77 percent of the region abnormally dry or in drought, which was 1 percent more than at the start of the month (Figure 8). The most intense drought conditions remained parked over Iowa, with 35 percent of the state in extreme (D3) drought on the U.S. Drought Monitor map. Drought intensified in southwest Iowa and along a swath from southern Missouri to northwest Ohio. Conditions improved slightly in central Minnesota, far western Missouri, and the northern half of Illinois.

Severe Weather

A strong cold front raced east across the country on December 9. This, combined with anomalous moisture and warmth ahead of the front, provided the necessary ingredients for severe weather, including tornadoes, across Kentucky (Figure 9). Hundreds of trees were snapped or uprooted in Todd and Logan counties (south-southwestern Kentucky) along with damage to outbuildings, homes, and powerlines.