Rainwater has the virtue of providing sustainable water resources and, with proper management, minimizing natural disasters such as flood and drought. Recently rainwater has occupied the attention as both cooling and heating source as well as the restoration of a water cycle. In this study, a rainwater circulation cooling system (RCCS) was used for cooling the cattle shed on a dairy farm in hot weather. When RCCS was operated for three hours in the afternoon from 12:00 to 15:00, the inside temperature of average 27.9 ℃ was lower than the ambient average 28.7℃. In contrast, when RCCS was not operated in the afternoon, the inside temperature of average 29.5 ℃ was higher than the ambient one of average 28.1 ℃. Temperature decrease reached about 2.6 ℃ due to RC CS operation compared with no RCCS operation at the hottest time of a day. Thermal regime of the rainwater tank installed underground was also investigated. It shows that a rainwater storage tank has a possibility to function as a cooling source in the summer. These results indicate that rainwater is able to be considered for a range of uses, including energy saving as well as prevention of flood and drought.