Ask any corn farmer if his crop "likes it cool"

Global warming will allegedly hit corn yields, costing the US over a billion dollars annually

“Corn likes it cool, but global warming is raising temperatures across the nation,” said Environment America Global Warming Advocate Timothy Telleen-Lawton. “Hotter fields will mean lower yields for corn, and eventually, the rest of agriculture.”

HowStuffWorks "Growing Corn"

Corn can be grown in any region, but the time it will take to mature depends on the amount of heat it gets. Corn doesn't really hit its stride until the weather warms up.

Lesson 1b: Corn Growing Degree and Applications

(1) That 86o F is the highest temperature considered. Why 86o F? The crop has its ideal growth at 93 [degrees] F. Why not 93o F? Seldom do we have ideal conditions for aeration, for fertility, and for water availability to the crop. As the temperatures get higher, the crop's demand for water may become higher. At a higher demand for water, the crop may come under water stress. In the Midwest, on the average, water stress begins at about 86o F. So we do not consider 93o F optimum unless everything is perfect. We consider 86o F the optimum temperature for crop growth.