Lack of an adequate water supply throughout the growing season is considered to be the major limiting factor to dryland cotton yields on the Texas Southern High Plains. Over the past 25 years, yields have had large year to year variation but the trend has been essentially a static yield. We gathered daily rainfall and temperature data from NOAA for the 1968 - 1992 period for each county in the Southern High Plains. Rainfall was developed to reflect stored water, growing season, critical growth periods and monthly supplies. Temperature data were used to develop heat units, high and low temperature thresholds. Regression analysis was performed in an effort to determine the extent to which these weather parameters control dryland cotton production, or, more importantly, to determine how much influence the individual producer is able to exert upon lint yield. Multiple regression revealed that in most cases less than 50% of the yield variation can be explained by a combination of weather factors. The other 50% of the yield variation is subject to management.