CHAMPAIGN, Ill. – Soil temperatures in Illinois have been above normal for most of the winter, according to Jennie Atkins, Water and Atmospheric Resources Monitoring (WARM) Program manager at the Illinois State Water Survey, Prairie Research Institute, University of Illinois.

For the period of December 1 through February 21, soil temperatures at 4 inches under bare soil averaged 36.7 degrees F across Illinois, 2.6 degrees above the long-term average and 2.9 degrees higher than last winter.

Soil temperatures this winter have fluctuated with air temperatures. The highest temperatures were reported in December with a statewide monthly average of 42.7 degrees or 6.8 degrees above average. Temperatures averaged 33.4 degrees in January, only 0.2 degrees above average, but have climbed slightly so far in February to an average of 35.1 degrees.

Winter soil temperatures have been above average throughout the state. The highest temperatures have been in southern Illinois where stations have averaged 40.3 degrees so far this winter, 3.3 degrees above the long-term average. Northern Illinois has had the coolest soil temperatures with a winter average of 34.4 degrees, still 2.7 degrees above average.

Soil temperatures at depths of 2 inches under bare soil have had larger fluctuations resulting in a slightly cooler winter average of 36.1 degrees. Temperatures under sod have been warmer with averages of 38.4 degrees at 4 inches and 38.6 degrees at 8 inches.

The third week of February saw a rise in both air and soil temperatures. As air temperatures rose into the 70s, highs ranging from 67 degrees at 2 inches under bare soil to 52 degrees at 8 inches under sod were recorded.

The Illinois State Water Survey’s WARM Program collects hourly and daily weather and soil information at 19 stations across the state. Daily and monthly summaries can be found at the WARM website (http://www.isws.illinois.edu/warm/) and in the Illinois Water and Climate Summary (http://www.isws.illinois.edu/warm/climate.asp).