Rewari has a dry, semi-arid climate. The mean minimum and maximum temperature range from 6 °C to 41 °C during January (winter) and May–June (summer) respectively. The summer temperature can go up to 46 °C from May to July. Winter is from November to February and the temperature can fall to 2 °C in December and January. The temperature was recorded as 0 °C on 12 January 2012 and 31 January 2012.
Rain falls from July to September. A little rain is experienced during winter also. Average annual rainfall in Rewari city is 553 millimetres (21.8 in). Rain-fed Sahibi River that originates in Rajasthan passes through Rewari and falls in Najafgarh lake in Delhi. Extremely heavy rains in 1978 flooded Sahibi (and Rewari) which in turn flooded Delhi. A barrage was then constructed at Masani village on junction of NH8 and NH71B to impound the water coming from Rajasthan. However, the barrage has hardly collected any water as the rains have not been heavy for the last 30 years and Rajasthan has built check-dams upstream on Sahibi. A canal has been constructed in 2009 to carry excess rain water to the barrage to recharge the ground drinking water for Rewari town. The canal takes off from the existing canal near the Kendriya Vidyalaya, Rewari
