Key Points

Climate is the sum total of weather conditions and variations over a large area for a long period, typically more than thirty years. Weather refers to the state of the atmosphere over an area at any single point in time.

The climate of India is described as the 'monsoon' type. The word 'monsoon' is derived from the Arabic word 'mausim' and refers to the seasonal reversal of wind direction during a year.

There are six major factors that control the climate of any place: latitude, altitude, pressure and wind system, distance from the sea (continentality), ocean currents, and relief features.

The Tropic of Cancer divides India into tropical and subtropical zones. The Himalayas prevent cold Central Asian winds from entering India, resulting in comparatively milder winters.

As the distance from the sea increases, its moderating influence decreases, leading to extreme weather conditions. This is known as continentality, characterized by very hot summers and very cold winters.

The Coriolis force, caused by the Earth's rotation, deflects winds to the right in the Northern Hemisphere. This force is responsible for the unique pressure and wind conditions that create India's monsoon.

Four main seasons can be identified in India: the cold weather season (winter), the hot weather season (summer), the advancing monsoon (rainy season), and the retreating monsoon (transition season).

From mid-November to February, northeast trade winds prevail, leading to a dry season. A key feature is the inflow of cyclonic disturbances from the west, causing winter rains ('mahawat') in the northern plains.

From March to May, this season is characterized by strong, hot, dry winds called 'Loo' in northern India. It also sees localized thunderstorms like 'Kaal Baisakhi' in West Bengal and 'mango showers' in Kerala and Karnataka.

Beginning in early June, the south-west monsoon winds bring abundant moisture and widespread rainfall to the country. Mawsynram in Meghalaya receives the highest average rainfall in the world.

The monsoon has a tendency to have 'breaks' in rainfall, meaning it has wet and dry spells. These breaks are related to the northward or southward movement of the monsoon trough.

During October and November, the monsoon trough weakens and withdraws. This period is marked by clear skies and a rise in temperature, leading to a condition known as 'October heat'.

During the retreating monsoon, low-pressure systems shift to the Bay of Bengal, causing cyclonic depressions. These cyclones bring heavy and destructive rainfall, especially to the eastern coasts like the Tamil Nadu coast.

India has extreme variations in temperature and precipitation. Summer temperatures reach 50°C in Rajasthan, while winter temperatures in Drass can be as low as minus 45°C. Rainfall varies from over 400 cm in Meghalaya to less than 10 cm in Ladakh.

Despite regional variations, the monsoon acts as a unifying bond for the Indian subcontinent. It provides a rhythmic cycle of seasons and the water necessary for agriculture, around which the entire life of the people revolves.