A cool wet spring followed a wet fall and winter. There were days in late April and early May suited to field work and planting. Rain patterns set in, delaying planting into the middle to late May. Then deluges of rain arrived after the first week of June. About a 200-300% increase in rainfall occurred in June, up to 9-12 inches, over Ohio, Indiana, Illinois, and Missouri, into southeast Nebraska. Widespread precipitation fell for 23 days. Some rains were torrential downpours with flash flooding, hail and wind damage. Temperatures were about normal. July was also wet but cooler. Rains continued for another three weeks, about 6-7 weeks of continuous rain since June. These conditions produced several stresses on the corn crop, especially later plantings. These stresses had an impact on the corn crop.
This Technical Bulletin explains these stresses on the the corn crop of 2105.
Tech_266 - Impact of a Wet Spring and Summer on the Corn Crop