"Combined with cooler temperatures, wet April conditions led to widespread corn planting delays in the northern two-thirds of the state, where precipitation averaged 4.05 inches (0.46 inches above normal) and up to 5–7 inches at some locations. April temperatures averaged 49.5°F statewide (2.7°F below normal), and statewide precipitation was 3.75 inches (just 0.05 inches below normal), based on preliminary data. Southern Illinois was drier, averaging 3.38 inches (0.74 inches below normal), and planting there is further along," says State Climatologist Jim Angel of the Illinois State Water Survey (http://www.sws.uiuc.edu), a division of the Illinois Department of Natural Resources.
"Illinois is still recovering from the early April hard freeze when temperatures dropped to the low 20s and upper teens statewide after the 6th warmest March on record since 1895. Those warm March temperatures 6.5°F above normal promoted early and rapid development of fruit crops and winter wheat, leaving them extremely vulnerable to the extended period of cold temperatures on April 6–8. While not record breaking, this early April cold weather was somewhat rare, and occurs roughly once every ten years on average. It's an excellent example of how together two unusual weather events can exceed damage (including destroying southern Illinois' peach and apple crops) of individual events," notes Angel.
The National Weather Service May outlook calls for an increased chance of temperatures above normal with precipitation above, below, or near normal. The May–July outlook calls for both temperatures and precipitation above, below, or near normal.
"Conditions in May should be more favorable for planting as warmer temperatures increase the chance for dry fields between rain events," concludes Angel.
Disclaimer: Data used for all statistics provided herein are from the Midwestern Regional Climate Center and are based on preliminary data.