Technical Abstract: Expansion in cotton (Gossypium hirsutum L.) production in the Ogallala Aquifer Region can be tied to early maturing varieties, rising energy costs, and declining water levels in the Ogallala Aquifer. However, the feasibility of growing cotton considering the availability of heat units in this region has not been determined. In this study, a 30-year (1971-2000), county-wide daily maximum and minimum air temperature database was used to assess heat unit availability for cotton production in the Ogallala Aquifer Region. The time of planting, to initiate heat unit accumulation during the growing season, was determined based on the estimated daily minimum soil temperature from corresponding air temperature data. A set of regression models developed for this purpose was found useful. Long term annual averages and exceedance probability curves for total heat units (THU) at 1-year and 2-year return periods were developed and used to identify counties that are suitable for cotton production. Comparison between the scenarios indicates that long-term THU averages are similar to that with 2-year return period. Of the 131 counties evaluated, 105 counties received 1000 (oC) or more heat units during the growing season at least once every two years. Results indicate that cotton is a suitable alternative crop for all counties in the Texas and Oklahoma Panhandles and the majority of counties in southwest Kansas. However, management uncertainties on irrigation efficiencies, soil type, fertilizer and pest management practices, and planting and harvesting schedules may require further consideration for determining the feasibility of cotton production in the Ogallala Aquifer Region.