Impact of Monthly Weather Variables on Long Term Yield Trends In Midwest Counties.

Corn and soybean yield progress trends in the Midwest are normally reported as if the growing conditions were uniform across the entire region.  The National Agricultural Statistical Service (NASS) yearly county surveys allow to characterize yield progress trends at county scale. In recent years monthly weather dataset have been presented in the form high resolution rasters. This study analyzed how yield trends in a county scale have been impacted by monthly minimum temperature, maximum temperature as well as precipitation during the growing season since 1970. The analysis aim is to explain what proportion year to year variation can be attributed to monthly weather variation in a county by county basis.