We found that only the winter drought treatment had a significant effect on the vegetative growth of three representative species in the plant community (Stipa oryzopsis, Ceratoides lanata, Gutierrezia sarothrae). Winter drought reduced plant water water potentials and gas exchange rates throughout the year and in all species, while the effects of summer drought were noticeable only for very short periods of time following rainfall events and not in all species. We conclude that overall winter precipitation far outweighs the importance of summer precipitation in sustaining this plant community, although average spring/summer precipitation is about equal to average fall/winter precipitation. However, due to the large seasonal temperature variation in this cold desert ecosystem (with a monthly mean of between -2.3 and 25.6 C), cold season precipitation can accumulate in deeper soil layers and remain available as a water source to plants until the end of summer, while an estimated 90% of all warm season precipitation is lost by evaporation and is of no use to plants.