Evaporation rates closely follow the climatic seasons, and reach their peak in the summer months of April and May and the central areas of the country display the highest evaporation rates during this period. With the onset of monsoon, there is a marked fall in the rate of evaporation. The annual potential evaporation ranges between 150 to 250 cm over most parts of the country. Monthly potential evaporation over the Peninsula increases from 15 cm in December to 40 cm in May. In the North-East, it varies from 6 cm in December to 20 cm in May. It rises to 40 cm in June in West Rajasthan. After the onset of monsoon potential evaporation decreases generally all over the country.