Taking into accounts variations in the elements of climate, i.e. changes in air temperature, amount of rainfall, changes of air current, etc., the climate of India can be classified into 4 (four) seasons, such as:
1. Summer (from March to May): During the three months from March to May it is summer in most parts of India. From the beginning of March as the Sun after crossing the equator, approaches the Tropic of Cancer, the temperature increases. Generally, the northern part of India experiences very experiences high temperature during May, while April is the hottest month in southern India. The normal temperature recorded in this time in generally 30°C. But, at some places in the plateau region the temperature rises to 40°C and in the Himalayan mountain region, it remains near about 20°C.
2. Rainy season (June to September): The rainy season in India begins generally from the second week of June and continues up to the second week of October. From the second week of June humid monsoon enters various parts of India in the south-west direction from the Bay of Bengal and causes rainfall everywhere in the state. The south-west monsoon causes heavy rainfall. The Northern states of India generally receives less rainfall than the south Indian states.
3. Autumn season (from October to November): From the beginning of October, monsoon begins to recede from this country and consequently rainfall becomes frequent. So this period is also called the “season of return Monsoon” or the “Post-monsoon”. The sky generally remains clear in most parts of the country. Though the rainy season is no longer there, yet, due to the cyclone coming from the Bay of Bengal, occasionally violent storms and rainfall are observed.
4. Winter season (from December to February): During the period from December to February there is winter season in India. In this time the sun exists just above the Tropic of Capricorn and sunlight falls obliquely on various places of India and as a result temperature begins to decrease. The temperature is lowest during the months of January and February. Also during this time clouds and dry North-East Monsoon passes over different regions of India and temperature is decreased considerably. But in Himalayan area the temperature is much lower (between 5°C and 10°C). But sometimes cyclone (coming from the West) causes storm and rainfall which is known as Western disturbance.
Note: The India Meteorological Department (IMD) has also specified four seasons in India, viz, summer, rainy, autumn, and winter (source: wikipedia). However, astronomical and other traditions of India divides the twelve calendar month into six seasons, viz, summer, rainy, early autumn, late autumn, winter, and spring.