Colder weather led to cooler than normal soil temperatures during the first half of April in Illinois, according to Jennie Atkins, Water and Atmospheric Resources Monitoring Program manager at the Illinois State Water Survey, part of the Prairie Research Institute at Illinois.
Temperatures at depths of 4 inches under bare soil averaged 45 degrees during the first half of April, 5 degrees below the long-term average and 11 degrees lower than last year. Soils have remained above freezing, although there have been daily low temperatures in the 30s.
At the start of April, soil temperatures were in the 40s, but rose the second week of the month with a high of 55 degrees on April 13. Cooler weather over the weekend caused soil temperatures to decrease. Soils averaged 46 degrees on April 15, with daily highs into the 50s and lows in the mid-30s.
Similar patterns occurred at 2 and 8 inches, which averaged 46 and 49 degrees, respectively, on April 15.
Soil moisture declined for most of the first two weeks of April. Levels at 4 inches fell 10 percent in the first 13 days. However, rain last weekend caused soil moisture to increase throughout the state to an average of 0.39 water fraction by volume on April 15, with soils at or near field capacity for most of the monitored locations.
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 and in the Illinois Water and Climate Summary.