Technical Abstract: Renewed interest in cotton production in the Ogallala Aquifer region can be tied to development of cold resistant/early maturing varieties, and declining water levels in the Ogallala Aquifer. However, the feasibility of growing cotton considering thermal characteristics of the region has not been determined. In this study, we used a county-wide daily air temperature database (1971-2000) to assess thermal suitability for farming cotton in the Ogallala aquifer region. For this purpose, the heat unit based county-wide exceedance probability curves for potential cotton yield were developed and identified counties that have the potential to grow cotton at 1- and 2-year return periods. Out of 131 counties in the study area, 105 counties have the potential to grow cotton with lint yield more than 500 kg/ha. Cotton yield potential were relatively higher for counties in the Southern High Plains and counties in the eastern half of the study area. Evaluation of county-wide potential cotton yield indicate that yield goals based on a 2-year return period may improve the chances of better profits to producers than yield goals with 1-year return period. However, management uncertainties on irrigation efficiencies, fertilizer and pest management, and planting and harvesting schedule may require further consideration for estimating potential cotton yield. Nevertheless, these results show that cotton is a suitable alternative crop for most counties in southwest Kansas and all counties in Texas and Oklahoma Panhandles. Also, significant reduction in water withdrawals from the Ogallala Aquifer for irrigation is possible if producers were to switch 50 percent of their corn acreage to cotton in counties that have yield potential more than 500 kg/ha. Information derived from this study is of interest to producers and commodity groups, crop insurance companies, and water resources management agencies.