Three seasons are markedly noticed in the Reserve, the dry, the wet and the cold. The cold season starts in November and lasts up to mid-February; later the hot season commences and lasts up to middle of June. The coldest months are December and January and the hottest months are March and April. The wet season starts in middle of June, though heavy pre-monsoon showers fall in April and May. The wet season lasts up to September. There is a break in the wet season in September and then again from October middle to November middle, the North-East monsoon showers will present themselves.
The climate is quite hot and dry in summer; the heat is relieved by pre-monsoon showers. The Reserve, on the whole, is generally healthy except in the South-Western portions of Beerambadi, Ainurmarigudi and Begur.
The temperature of the reserve is generally moderate. The mean annual temperature of the reserve is 24.160o C with maximum temperature of 29.660o C and minimum temperature of 18.660o C. The nights are cold in winter in pockets like Bandipur, Moolehole and Himvad Gopalaswamy hills. The sun is little strong in summer.
The Reserve gets heavy pre-monsoon showers in late April and May and these rains are generally accompanied by lightning and thunder. The South-West Monsoon starts by mid June and lasts up to September. The precipitation is continuous and heavy in July. The North-East monsoon brings in lighter rains. The heavy rainfall tracts adjoin the Kerala border to the South-West portion of the Reserve(Begur and Ainurmarigudi). The rainfall decreases towards the eastern and northern portions of the Reserve. The bulk of the rainfall is got from the South-West monsoons between June and August. September has comparatively low rainfall; but late October and November again bring in more rain. The rainfall at Kalkere in Ainurmarigudi range is more than 1270 mm. The average annual rainfall ranges from 1270 mm at Kalkere to 914 mm at Bandipur. However, on the Western part of the Reserve (parts of Begur and Ainurmarigudi) the rainfall is more and is less in Moyar state forests. During the year 2005 Bandipur has received 1427 mm Rainfall.
Storms and Cyclones are very rare and there are no records of damage caused by them. South-West monsoon is generally accompanied by wind from western side from June to August. Velocity of wind is high on the top of Gopalaswamy hills.