The area lies in the moist tropical zone. The average day temperature varies from 12oC to 21oC from November to February, between 27oC to 32oC from May to September, between 24oC to 27oC for the rest of the months. The highest recorded temperature was 39oC (102.5oF) in 1899 and lowest was 2oC(36oF) in 1887 (Ref: 5th Working Plan of Buxa Division). There is an appreciable variation in day & night temperature throughout the year. Some times winter nights are too severe. From July to September, the days & early evenings are moist & hot and indeed oppressive, however, nights are always cooler.
South – West monsoon is the main source of rainfall. The Reserve receives maximum rainfall from mid June to September. The rainfall is very high during the month of June, July & August. It subsides from the early September and disappears during the first week of October. December is the driest month with minimum rainfall. March receives maximum of winter rain. Pre-monsoon showers accompanied by hail & thunder storm occur in the month of April to May.
The average annual rainfall in the Reserve is about 4100mm. , increasing a little towards North. Along the foot hills the rainfall varies according to the configuration of the hills; on the outer ranges of the hills it reaches around 5000mm.per year. The average annual rainfall at Rajabhatkhawa is 3750mm. while that in Buxaduar (altitude 780 mt.) is 5600mm. Highest rainfall in a day in last 10 years was recorded as 992 mm. on 19th July 1993. It caused devastating flood in Alipurduar.
As the Reserve is located in the foothills of the outer Himalayas, it remain adequately humid throughout the year. Maximum relative humidity varies between 80% – 95% , seldom below 75% with a maximum in June to September and minimum in December to February.
The Reserve does not experience any high gale possibly due to existence of large chunk of dense forest cover. However, severe storms sometimes accompanied by hail occur in the months of April & May and rarely in September and October.During 1942 – 43 a heavy cyclone hit the Reserve causing enormous damage. It uprooted numerous trees and broke the crowns in good numbers. Such cyclones are not frequent but mild form of cyclone is almost an annual features causing lot of cyclone damage trees.
Frost, Dew & Fog :
From November to February the nights are very cold with much frost and dew and in low lying areas a dense fog lingers often even beyond 9.00 a.m. From March to the onset of monsoon fog & frost are absent but dew is deposited until April.
The hill streams are always unpredictable. Devastating floods have been reported during 1950, 1952, 1954, 1968 and 1993 causing massive damage to the forests. The flood in Rydak river in 1968 have played havoc in the central Rydak and Marakata blocks. It damaged forest quarters of Teamari Beat. It left long trail of sandy beds on either side of the main course. Construction of an embankment (15 Km.) by the Irrigation Deptt., on its Western bank minimised the chances of further damage. Construction of another bundh across the old course by I & W Deptt. in 1974 – 75 has completely eliminated the possibilities of flowing of this river through earlier damaged areas.
Heavy rains occurred on 19th July (992mm) 1993, as a result of which the Reserve suffered heavily. Entire Alipurduar Subdivision suffered heavily as road connections were cut off, wooden as well as concrete bridges were washed out. This flood caused havoc to vegetation and forestland.