This paper examined the role of weather, yield, and prices on the planting decisions of crop farmers in Ontario. Increases in the length of the growing season, and not its intensity as measured by average maximum temperature, were found to increase the average yield for corn, soybeans, and winter wheat. Increases in the variance of temperature and precipitation decrease mean yield for those crops while increasing the variance. Climate change projections of longer growing season with more extreme events will have offsetting impacts on yield with the longer growing season having the dominant effect.