And then it rained, and rained some more. Heavy and severe thunderstorms were generated by a lingering front that parked over Iowa for the bulk of the week. Consequently, little field work was accomplished in most fields in Iowa. In addition to the heavy rains, the clash of air masses is evidenced by the degree day accumulations for the week. Southeast Iowa gained 40 base-50 degree days over average, while Northwest Iowa was about on average. The 40 degree days represents approximately 2 days of normal weather for crop growth, so it is like getting a 9 day work week in for growing plants.
Iowa State University
Integrated Crop Management News, "June is Bustin' Out All Over!" (2008). Integrated Crop Management News. 890.