In a year when many state records were broken, 2015 ended with historically warm temperatures and well above-normal precipitation, leading to the warmest and wettest December on record for the Midwest, according to the Midwestern Regional Climate Center (MRCC) at the Illinois State Water Survey (ISWS).
Average Temperature (F): Departure from
1981 to 2010 Normals
The Midwest’s preliminary average December 2015 temperature was 36.7 degrees F, which was 10.7 degrees above normal. The previous record was 34.1 degrees in 1923.
The record warmth was widespread across the Midwest as all nine states in the MRCC region experienced their warmest December on record. Kentucky, Michigan, Ohio, and Wisconsin broke their previous records by more than 3 degrees.
Record wet conditions also occurred as the Midwest received a preliminary total of 5.01 inches of precipitation in December 2015. The previous record was 4.42 inches in 1982.
Iowa and Wisconsin experienced their wettest December on record. Precipitation was more than 3 inches above normal and more than an inch above the previous record in both states.
Illinois, Missouri, and Minnesota experienced their second wettest December on record, while all nine states in the MRCC region ranked among the top-ten wettest. A majority of the precipitation in Illinois and Missouri fell in the second half of December, leading to major flooding on the Mississippi, Missouri, and Illinois rivers and many of their tributaries.
