Here are the patterns of precipitation and temperature departures across the Corn Belt for October so far. The eastern half of the Corn Belt experienced both wetter and cooler than average conditions for the month. Meanwhile, the western Corn Belt was both drier and warmer than average.
And here is the corn harvest progress by state, using data from the USDA and mapped by the Iowa Environmental Mesonet. Some of the delays in the eastern Corn Belt are likely due to the wet October (and wet September). However, the delays in the western Corn Belt are likely due more to the late start to the growing season and the cool weather during the growing season.