Excessive pumping of water for irrigation and low recharge rates are decreasing water levels in Ogallala aquifer at an alarming rate. There is a need to select crops that are more water efficient for sustaining the aquifer. Corn is the major supplier of green forage, silage and grains to the large beef and dairy industry in the region. Sorghum is a drought tolerant and more water use efficient alternative to corn. However, sorghum is a warm season grass and needs a warmer environment compared with corn, particularly soil temperatures for good germination. A scientific evaluation of sorghum thermal suitability in Ogallala underlain region based on long term weather data is urgently needed. Temperature data from 1970-2000 from 232 counties were used to calculate growing degree days (GDD) for the base temperature of 10°C. Four seeding date scenarios from May 1 to June 15 in 15 day increments were used for the calculation. Suitability of three maturity classes of sorghum with GDD requirements of 1525 (late), 1375 (medium) and early (1200) were assessed in each seeding date scenario. Growing season heat accumulation in the study area ranged from 692 to 2652. Based on growing season heat accumulation, about 85% of counties were suitable for growing any maturity class of sorghum. However, delaying the time of seeding imposed restriction on type of sorghum grown and only 60% of counties could grow any type of sorghum if seeded on June 15^th. About 3% of all counties could not grow sorghum if time of seeding was delayed beyond June 15^th. If seeded on May 1^st, early maturing sorghum cultivars will help in extending thermal suitability of counties by 14%, which further increased to about 38% under delayed seeding. Exceedance probability analysis was used to assess the risk associated with heat accumulation in Ogallala counties.