Climate change is the most challenging issue of our time. While climate change is often portrayed as a global phenomenon, the real impacts of climate change are felt at the local level. Changes in climatic conditions directly affect the level of precipitation which is very important for crop production in Ontario. How do changes in climate affect corn and soybean yields at the county level in Ontario? This question is addressed in this paper by estimating the effects of climatic and economic factors on yields of grain corn and soybean in three selected counties in Southwestern Ontario employing data from 1950 to 2013. The results demonstrate that the effect of precipitation during growing season on yield is positive and statistically significant and it is consistent across the selected counties. The effects of solar energy on crop yields vary across counties. Yields of both crops increase as crop price increases and decline as the price of fertilizer increases. Finally, developments in technology have a strong effect on enhancing yield for both crops. The climatic factors have a larger impact than the effects of economic factors on corn yields at the county level. The reverse, however, appears to be true for soybean production at the county level in Ontario. The policy implications of the results are also discussed.