Key Points

Weather is the momentary state of the atmosphere, changing quickly within a day or week. Climate refers to the average of weather conditions over a longer period, such as 50 years or more.

Monsoon connotes a climate associated with a seasonal reversal in the direction of winds. India has a hot monsoonal climate, which is common in south and southeast Asia.

Despite an overall monsoon type, India has significant regional climatic variations. For example, summer temperatures can touch 55 degrees Celsius in Rajasthan, while winter temperatures in Leh can drop to minus 45 degrees Celsius.

India's climate is controlled by several factors, including its latitude, the Himalayan Mountains, the distribution of land and water, distance from the sea, altitude, and relief features.

The Himalayas act as an effective climatic divide by protecting the subcontinent from cold northern winds. They also trap the monsoon winds, forcing them to shed moisture within India.

The ITCZ is a low-pressure zone at the equator where trade winds converge. Its northward shift in summer over the Gangetic plain forms the monsoon trough, which attracts the monsoon winds.

The sudden arrival of moisture-laden winds, associated with violent thunder and lightning, is termed the 'burst' of the monsoon. It typically reaches the Kerala coast by the first of June.

The southwest monsoon approaches India as two distinct branches. They are the Arabian Sea branch and the Bay of Bengal branch.

The windward side of the Western Ghats receives very heavy rainfall from the Arabian Sea branch. The leeward side, including the Deccan Plateau, remains dry and is known as a rain-shadow area.

During the cold season, shallow cyclonic depressions from the Mediterranean Sea cause winter rainfall in northwestern India. This precipitation is highly beneficial for rabi crops like wheat.

The hot weather season features hot, dry winds called 'Loo' in the Northern plains. It also sees pre-monsoon showers like 'Mango Showers' in Kerala and 'Kalbaisakhi' or Nor Westers in Bengal and Assam.

The months of October and November are known for the retreating monsoon. This period is marked by clear skies and a rise in temperature, creating oppressive weather known as 'October heat' in north India.

During the retreating monsoon season, winds pick up moisture over the Bay of Bengal. They cause heavy rainfall over the Tamil Nadu coast, southern Andhra Pradesh, and southeast Kerala.

El Nino is the appearance of a warm ocean current off the coast of Peru every three to seven years. It is linked to weaker monsoon rainfall and drought conditions in India.

Rainfall in India shows great spatial variation. High rainfall areas (over 200 cm) include the Western Ghats and Northeast India, while inadequate rainfall areas (below 50 cm) include western Rajasthan and Ladakh.

The monsoon is the axis around which India's entire agricultural cycle revolves. The prosperity of Indian agriculture is highly dependent on timely and adequately distributed rainfall from the monsoon.