Soil Temperature at the 4-inch depth is important to crop establishment even though seed placement is usually at depths of less than 2 inches. Soil temperature of below 50F is important to responsible fall anhydrous application. The estimated county soil temperature in Iowa is derived from observations at 16 locations extrapolated to the 99 Iowa counties. The estimated county temperatures may be obtained at: http://mesonet.agron.iastate.edu/agclimate/soilt.php values in “red” are measured temperatures all others are estimates based on the observations.
Observed Soil Temperatures at other depths (4”, 12”, 24”, 48” ) can be viewed by selecting the depth from :
http://mesonet.agron.iastate.edu/agclimate/#tmpf
Freezing to depth in Iowa soils is most common when snow cover is scant during the coldest period of winter. Snow cover of 12” or more often results in reduced penetration of freezing temperatures in the soil.