Weather data (Rainfall and maximum daily temperatures, from 1900 to 2002, or from 1922 to 2002) during the corn growing season were analyzed using the Leeper, Runge and Walker (1974) corn model for 4 different tasseling dates and 3 different soils (Plant available stored soil moisture [PASSM] of 10, 17.5 and 25cm). Corn yields increased during this time interval for Urbana, IL; Lafayette, IN; Ames, IA; Columbia-Fulton, MO; Lincoln, NE; Columbus, OH; Brookings, SD; Ottawa and Manhattan, KS; Stillwater, OK; Sherman, TX; and Hillsboro, TX locations. Corn yield changes were near 0 during this time interval for Lansing, MI; Minneapolis, MN; Madison, WI; Kaufman, TX College Station, TX and Brenham, TX locations. Yields decreased during this time interval for Raymondville, TX and for soils with 10 cm of PASSM for Manhattan, KS and Kaufman, TX locations. The largest increase in corn yield during this time interval occurred for the Brookings, SD location. Four different tasseling dates were analyzed for each location (very early, early to average, average to late, and late). Yields were highest for very early and early to average tasseling dates for all locations. In the central and northern corn belt locations corn tasseling late encountered more favorable weather than corn tasseling during the average to late date. Southern locations had progressive and dramatic decreases in corn yield as tasseling dates progressed from early to late.