A test of whether minor production adaptations to climate significantly affect corn yields is the focus of this article. Cross-sectional, field-level corn data are used to analyze production across various climates. A 65°F change in temperature, when both adaptations to climate and the direct effect of weather are included, raised yields by 43.8 percent in areas with average July temperatures of 67°F and reduced yields by 69.6 percent in areas with average July temperatures of 76.5°F.