Expansion of cotton (Gossypium hirsutum L.) production in the Ogallala Aquifer region of the United States can be attributed to early maturing cultivars, rising energy costs, and declining groundwater levels. The feasibility of growing cotton relative to the availability of heat units (HU) in this region has not been determined. In this study, a 30-yr (1971-2000), county-wide, daily maximum and minimum air temperatures database was developed to assess HU availability in the region. The time of planting used to initiate HU accumulation during the growing season was based on the estimated daily minimum soil temperature at planting depth. Linear regression models to estimate daily minimum soil temperature at planting depth using air temperature were developed for each of the climatic regions in the study area. The growing season was terminated with the first freeze or 15 October, whichever occurred first, and this was considered the harvest date. Total heat units (THU) based on the long-term annual averages and exceedance probability of 0.99 (every year) and 0.75 (3 out of 4 yr) were estimated and used to identify counties that are suitable for cotton production. Of the 131 counties evaluated, 110 received 1000 (°C) or more HU in 3 out of 4 yr. Based on heat unit availability, cotton is a suitable alternative crop for all counties in the Texas and Oklahoma panhandles and for the majority of counties in southwestern Kansas. Management uncertainties, such as irrigation efficiencies, soil types, fertilizer and pest management practices, and planting and harvest schedules, may require further consideration to determine the feasibility of cotton production in the region.