Soil Temperatures in Illinois

With the arrival of spring, Illinois farmers are monitoring soil temperatures for decisions in the field. And the soil temperatures are on the rise.

The ISWS Water and Atmospheric Resources Monitoring (WARM) Program records soil temperatures at 4 and 8 inches under grass at 19 sites across the state. In addition, 4-inch bare soil temperatures are computed to represent a cultivated field. These data are available in map and tabular form for the past 7 days at http://www.isws.illinois.edu/warm/soiltemp.asp.

As of April 6, the 4-inch soil temperatures under grass during the day are into the upper 40s in northern Illinois, the low to mid 50s in central Illinois, and the mid 50s in southern Illinois. At night they are cooling off by about 4 to 6 degrees.

The statewide soil temperatures give a general idea of conditions; however, soil temperatures in an individual field will depend on factors such as soil moisture and tillage practices. Also, soil temperatures at the surface will warm up and cool off faster than in deeper layers.

About Jim Angel

I have been the state climatologist for Illinois since 1997 and have worked at the Illinois State Water Survey since 1984.
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2 Responses to Soil Temperatures in Illinois

  1. Bob Lawless says:

    Jim Angel,
    How much of an effect does rainfall have on change in soil temperature? Does a wet soil warm/cool faster or slower than a dry soil?
    Will you have the 4″ soil temperature maps with the gradiant lines available like you did last year?

  2. Jim Angel says:

    Yes, soil moisture plays a key role in soil temperature. Wet soils tend to warm up more slowly than dry soils. We have soil temperatures from 19 sites in Illinois posted at http://www.isws.illinois.edu/warm/soiltemp.asp
    They aren’t contour maps but the individual values are plotted to give you an idea of the variability. At some point, we may reinstate the contour maps or shaded maps. We are in the process of redoing many of the products on the web site.

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