80% of Iowa’s corn is grown north of Interstate 80, none to speak of irrigated. Heat stress there will reduce yields a bit, but it’s hardly a crisis.
The US might produce only 12+ billion bushels instead of 13+ billion bushels.
Given record world grain production, starvation isn’t just around the corner.
Here’s a link to what the Iowa farmers are saying. The farmers I know are struggling
http://www.huffingtonpost.com/2012/07/12/us-drought-corn_n_1666591.html