The state falls under the Tropical Monsoon climatic region. The Tropic of Cancer cuts across the state passing through the middle of the Ranchi City. The average temperature of the state is 25° C, which varies greatly because of varying heights of different plateaus mentioned above. The average temperature of the Pat region is below 23° C while rest of the state records average annual temperature between 23 and 26° C except the eastern part of Santhal Pargana region, East Singhbhum, Garhwa, Palamu and the northern part of Chatra districts where it is above 26° C. There are extremities in climate in the state in two seasons- summer and winter.
The hottest areas are found towards the north western part of the state (Daltonganj), around Jamshedpur and Dhanbad cities having more than 40° C temperatures. Similarly, the state gets affected by the cold waves with less than 5° C temperature and reeling cold. The average annual rainfall in the state is 1400 mm with more than 4/5th rainfall between June to September. It also gets rainfall from the branch of monsoon from the Arabian Sea. There are also variations in rainfall varying from below 1200 mm to 1800 mm.
There are five climatic regions in the state.
One, North Eastern and North Central Plateau Region (Western part of Santhal Pargana region, Giridih, Kodarma and Northern Hazaribagh);
two, Upper Chotanagpur region (Pat region, Ranchi Plateau, Gumla and the plateau region of outer Chotanagpur spread in Simdega);
three, South Eastern Region (East Singhbhum, Saraikela and West Singhbhum);
four , Eastern Region (Sahibganj, Pakur, eastern Deoghar, eastern Jamtara and north eastern part of Saraikela); and
five, North Western Lower Plateau Region (Garhwa and Pala)