Varietal differences of switchgrass in growth and development, biomass yield and partitioning in response to temperature are not well documented. A study was conducted to quantify the effect of temperature on growth, development, and feedstock quality of switchgrass cultivars, and to determine differences between upland and lowland switchgrass. Two lowland (“Alamo” and “Kanlow”) and two upland (“Caddo” and “Cave-in-Rock”) cultivars of switchgrass were grown in pots filled with pure, fine sand in growth chambers. Four different temperature treatments of 23℃/15℃, 28℃/20℃, 33℃/25℃, and 38℃/30℃ with 14/10 hours day/night were imposed at four leaf stage. High temperature significantly decreased the biomass yield across all cultivars. Stem elongation rate (SER) and leaf elongation rate (LER) decreased at the highest temperature treatment but lowland cultivars had significantly higher SER and LER across the temperature treatments. Upland cultivars produced more tillers across the temperature treatment. Both shoot/root and leaf/stem ratios increased under the highest temperature in all cultivars, but upland cultivars partitioned more to the leaf and root at higher temperature. Concentration of cellulose decreased at the highest temperature but temperature had no effect on lignin concentration of leaf and stem biomass. In conclusion, although none of the cultivars studied showed strong tolerance to high temperature, differences were observed for many traits of switchgrass in response to temperature.