Purnea is known for its moderate climate; it has also remarkably earned its name as 'Poor's man's Darjeeling' due to its favourable climate. Purnea, with the highest rainfall in Bihar state, has a largely humid climate, with humidity rising to above 70%. A cold season, from November to February, is followed by a hot season from March to June. The monsoon season begins in early June and lasts until September, during which 82% of total annual rainfall falls.
January, the coldest month, has a mean daily minimum temperature of 5 to 10 °C and a mean daily maximum of 20 to 25 °C. Wind is typically light in the non-monsoon seasons but during the monsoon, storms and depressions originating in the Bay of Bengal cause heavy rain and strong winds
