The climate of India may be broadly described as tropical monsoon type. Its climate is affected by two seasonal winds — the north-east monsoon and the south-west monsoon. The north-east monsoon commonly known as winter monsoon blows from land to sea whereas south-west monsoon known as summer monsoon blows from sea to land after crossing the Indian Ocean, the Arabian Sea and the Bay of Bengal. The south-west monsoon brings most of the rainfall during the year in the country. It is now possible to make forecast about the monsoon rains successfully with developed models and trained manpower.
The Himalayan states, being more temperate, experience two additional seasons: autumn and spring. Traditionally, Indian notes six seasons, each about two months long. These are spring (Sanskrit- Vasanta), late autumn (Hemanta) and winter (Shishira). These are based on the astronomical division of the 12 months into six parts. The ancient Hindu calendar also reflects these seasons in its arrangement of months.
The Indian Meteorological Department (IMD) designates four official seasons:
1. Winter (From December to early April): The year's coldest months are December and January, when temperature average around 10-15 degree Celsius (50-59 Degree Fahrenheit)in the north-west; temperature rises as one proceeds towards the equator, peaking around20-25 degree Celsius(68-77 degree Fahrenheit) in the mainland India's south-east.
2. Summer or Pre-monsoon season (April to July in north-western India): In western and southern regions, the hottest month is April; for northern regions, May is the hottest month. Temperatures average around 32-40 degree Celsius (90-104 Degree Fahrenheit) in the most of the interior.
3. Monsoon or Rainy season (June-September): The season is dominated by humid south-west monsoon, which slowly sweeps across the country beginning in late May or early June. Monsoon rains begin to recede from North India at the beginning of October. South India typically receives more rainfall.
4. Post-monsoon season (October-December): It is also known as north-east monsoon in the southern Peninsula. In north-western India, October and November are usually cloudless.
The Monsoon climate is a characteristics property of south and south-east Asia and has influence over the economic activities of these regions. The Indian agriculture is considered a gamble against monsoon because agricultural activities over almost all parts of the India are very much dependent up on the monsoon rainfall. In fact, monsoon is the axis around which the Indian economy revolves.