The growing season weather in the corn, wheat and soybean production areas of the United States is an important determinant of the U.S. supply of these commodities. The weather and climatology literature strongly suggest that during the summer months there is a degree of persistence in the North American weather patterns. Given this nonrandom character of weather and given that the corn, wheat and soybean belts are geographically concentrated enough to be dominated by a regional weather phenomenon, their futures markets are hypothesized to reflect this assimilation of nonrandom weather information as nonrandom price fluctuations. An empirical test of this question is the subject of this paper.