Variation in the annual acre yield of corn, a major practical problem of the Corn Belt, is largely to be correlated with variations in climate. 55 sample counties were selected as the areal units of investigation. 35 climatic factors, most of them for monthly periods and for 1914-1932, were correlated with corn yields for the corresponding yrs. The resulting simple correlation coeffs., 1 for each factor in each co., were mapped and isoplethed. Multiple correlations involving as many as 7 climatic factors were run for 29 of the selected cos. Multiple and partial coeffs. of correlation also were mapped. Ca. half the factors investigated were significant in some part of the Corn Belt. Temp., on the whole, was more significant than precipitation. The coeffs. for any 1 factor frequently had a wide range in significance from one region to another. From a central area in which there is very little significant correlation with any factor studied, there is an increase toward the margins both in significance of the coeffs. and in no. of significant factors. On these bases the area was tentatively divided into forecast districts. Some factors in some divisions are significant enough to be decidedly helpful in forecasting corn yields.