Climate

What controls India’s climate, how the monsoon works, the four seasons, local storms and winds, and how rainfall is spread across the country.

Key ideas

• India’s climate is controlled by latitude, the Himalayas, the spread of land and water, distance from the sea, altitude and relief.
• In summer the ITCZ moves north over the Ganga plain; south-east trades cross the equator, turn south-west and arrive as the monsoon with a sudden “burst”.
• The monsoon has two branches: the Arabian Sea branch drenches the Western Ghats, and the Bay of Bengal branch moves up the Ganga and Brahmaputra valleys.
• Meteorologists recognise four seasons: cold weather, hot weather, south-west monsoon, and the retreating monsoon with its “October heat”.
• Local storms and winds: mango showers and blossom showers in the south, nor’westers (kalbaisakhi) in Bengal, and the hot, dry loo over the northern plains.
• Tamil Nadu gets most of its rain from the north-east monsoon; winter rain from western disturbances helps rabi crops in the north-west.
• A break in the monsoon is a dry spell of a week or more during the rainy season.

Remember

Watch out

• Saying Tamil Nadu gets its main rain from the south-west monsoon (it is in a rain shadow then).
• Counting 30 days after 1st June as 31st June: it is 1st July.
• Mixing up the loo (hot, dry wind) and nor’westers (evening thunderstorms).

Worked example