The climate in India is dominated by the seasonal monsoon, but regional differences in the micro-climate abound due to the varying topography and the influence of the oceans. Indeed, the presence of the Himalayas and the Indian Ocean lend the country characteristics of both a tropical climate and a continental one. The result is an extreme in temperature and moisture levels from the arid conditions of the Thar Desert to the rainforest climate of the Northeastern States. Similarly, temperatures vary from below freezing in the higher passes of the Himalayas to torrid heat on the Gangetic Plains. It is therefore difficult to generalize about the climate in India as a whole. Nevertheless, India does provide one of the best examples of a monsoon climate due to the distinct division between the wet and dry seasons.

The monsoon in India arises from the reversal of the prevailing wind direction from Southwest to Northeast and results in three distinct seasons during the course of the year. The Southwest monsoon brings heavy rains over most of the country between June and October, and is referred to commonly as the ‘wet’ season. Moisture laden winds sweep in from the Indian Ocean as low-pressure areas develop over the subcontinent and release their moisture in the form of heavy rainfall. Most of the annual rainfall in India comes at this time with the exception of in Tamil Nadu, which receives over half of its rain during the Northeast monsoon from October to November.

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The retreating monsoon brings relatively cool and dry weather to most of India as drier air from the Asian interior flows over the subcontinent. From November until February, temperatures remain cool and precipitation low. In northern India it can become quite cold, with snow occurring in the Himalayas as weak cyclonic storms from the west settle over the mountains. Between March and June, the temperature and humidity begin to rise steadily in anticipation of the Southwest monsoon. This pre-monsoonal period is often seen as a third distinct season although the post-monsoon in October also presents unique characteristics in the form of slightly cooler temperatures and occasional light drizzling rain. These transitional periods are also associated with the arrival of cyclonic tropical storms that batter the coastal areas of India with high winds, intense rain and wave activity.

As mentioned, rainfall and temperature vary greatly depending on season and geographic location and even within these, the timing and intensity of the monsoon is notoriously capricious. The result is a vastly unequal and unpredictable distribution over time and space. In general, the northern half of the subcontinent sees greater extremes in temperature and rainfall with the former decreasing towards the north and the latter towards the west. Rainfall in the Thar Desert and areas of Rajasthan can be as low as 200mm per year, whereas on the Shillong Plateau in the Northeast, average annual rainfall can exceed 10,000 mm per year. Similarly, temperatures vary from sub-zero in altitude during the winter months to 48C highs in mid-summer. On average, the mean maximum temperature during the coolest months in northern India is 21C and during the summer months between 38-43C. The extreme southern portion of the country sees less variation in temperature and rainfall. In Kerala, the temperature varies by only 2.5C around the annual mean of 27C and the total annual rainfall is 3,000 mm.