Soil temperatures have been rising throughout the first half of June, 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.
Soil temperatures at depths of 4 inches under sod averaged 77.7 degrees in Illinois on June 14, 4.7 degrees above the long-term average. Temperatures have risen an average of 8.4 degrees the first two weeks of the month.
Temperatures have been warmer under bare soil. At 4 inches, temperatures averaged 82.5 degrees on June 14, 9.2 degrees above normal. Daily highs were in the mid- to high 90s for most of the state.
Although soil temperatures have been rising, soil moisture levels have been declining. The first half of June has been dry, receiving 0.29 inches of precipitation, or 1.60 inches less than normal. This, in conjunction with the warm soils, has led to declining soil moisture across the state.
Levels at the 2-inch depths have decreased 25 percent between June 1 and 14 to an average of 0.21 water fraction by volume. Soil moisture increased in central Illinois on June 14 as storms moved through the area, but levels remain below the historical average.
Similar declines occurred at the 4-, 8- and 20-inch depths. However, soil moisture remains high at 39 and 59 inches with no significant changes.
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.