Champaign, Ill. - Warmer weather across the state has led to higher than normal soil temperatures, according to Jennie Atkins, Water and Atmospheric Resources Monitoring (WARM) Program manager at the University of Illinois' Illinois State Water Survey.
Soil temperatures rose steadily over the first half of April, increasing 11.5 degrees during the first 15 days. At depths of 4 inches under sod, temperatures averaged 54.9 degrees for the period, 4.4 degrees higher than the long-term average.
Temperatures increased across Illinois throughout the first half of April. Highs in the 60s were recorded throughout the state, reaching into the low 70s at several locations. Southern Illinois saw the highest temperatures with a regional average of 63.3 degrees on April 15. The lowest were in the north where temperatures averaged 57.6 degrees.
Higher temperatures were seen under bare soil for the month. At depths of 2 inches, temperatures average 56.9 degrees with highs into the mid-80s in southern Illinois.
Soil moisture peaked on April 5 when the state received just under an inch of rain. Since that time, soils have been steadily drying. Levels at 2 inches have declined 23 percent, on average, between the 5th and the 15th to a mid-month average of 0.33 water fraction by volume (wfv). The driest conditions were in west central Illinois where levels averaged 0.29 wfv on April 15, still significantly above wilting points.
Similar but smaller declines in moisture levels occurred at 4- and 8-inch depths. At depths of 20 inches and greater, levels remained high with statewide averages of 0.40 wfv and greater throughout the first half of April.
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).