Climate is as important as terrain in influencing population. Of all the climatic factors, twin elements of rainfall and temperature play the most important role in determining the population of an area. Man cannot go beyond the limits set by climate.

Extremes of climate discourage the concentration of population. Such climates include the too cold climate of Himalayas, and the too hot and dry climate of the Thar Desert. A moderate climate, on the other hand, is favourable for population.Of the twin factors of rainfall and temperature, rainfall is more effective in determining the distribution of population. It is generally said that the population map of India follows its rainfall map. Rainfall supplies sufficient water for agriculture which is the main occupation of Indian masses.

As we move from the Ganga-Brahmaputra Delta in the east towards the Thar Desert in the west, the amount of rainfall and consequently the density of population decrease. However, there are a few exceptions to this general observation.

The Assam valley in the north-east and the Circars coast on the Bay of Bengal has moderate density of population although these areas receive heavy rainfall. Similarly, southern face of the Himalayas is scarcely populated though this area receives sufficiently high rainfall.

Alternatively;

Some of the adverse factors such as steep slope, frequent floods, infertile soils and dense forests counterbalance the positive effect of rainfall. Increased use of irrigation facilities in north-west India comprising Punjab, Haryana and western Uttar Pradesh has resulted in higher concentration of population than normally expected considering the amount of rainfall received by this region.

Since India is a tropical country, temperature is fairly high and does not play as important a role as is done by rainfall except in extreme cases. On high altitudes, in the Himalayan region, climate is too cold beyond 2,000 m and population is sparse there. There is practically no population in areas over 3,000 m above sea level.