India's Four Seasons and the Southwest Monsoon

India's Climate, Seasons & the Monsoon

Most of India lies between the equator and the Tropic of Cancer (23.5°N).
Tropical location → hot summers, warm winters, high rainfall in most regions.
The Himalayas block cold Arctic winds from Central Asia → India warmer than other countries at same latitude.
Surrounded by sea on three sides → moderating influence on temperature.

Season	Months	Characteristics
Cold Weather Season (Winter)	December – February	Cool/cold; dry; NW winds; fog in north; pleasant in south
Hot Weather Season (Summer)	March – May	Very hot; dry; dust storms (NW); Loo (hot wind) in plains; up to 48°C
Southwest Monsoon (Rainy)	June – September	Heavy rain; brings 75–90% of India's annual rainfall; humid
Retreating Monsoon (Post-monsoon)	October – November	Monsoon withdraws; NE monsoon hits Tamil Nadu; cyclones in Bay of Bengal

Monsoon = seasonal reversal of winds.

Summer heating: Indian landmass heats up intensely (May–June).
Low pressure: Hot air rises over land → creates low pressure area over the Indian subcontinent.
High pressure over sea: Indian Ocean stays cooler → high pressure over ocean.
Winds blow from high to low pressure: moisture-laden winds from Indian Ocean rush towards land.
Coriolis effect (Earth's rotation) deflects these winds → they blow from SW direction.
Orographic rainfall: winds hit Western Ghats → forced to rise → cool → condense → heavy rain on windward (western) side.
Rain shadow: eastern side of Western Ghats receives much less rain (Deccan Plateau).

Branch	Path	Areas affected
Arabian Sea branch	Hits Western Ghats → Kerala → moves north along west coast	Kerala, Maharashtra, Goa, Gujarat; also crosses Vindhyas into MP/UP
Bay of Bengal branch	Enters NE India → moves west along Ganga plains	NE India (heaviest), West Bengal, Ganga plains, Rajasthan (weak)

Landmass cools down in October.
Low pressure over land weakens.
High pressure develops over land.
Winds reverse → blow from land to sea (NE direction).
Northeast Monsoon: picks up moisture from Bay of Bengal → brings rain to Tamil Nadu coast (Oct–Dec) — why Chennai gets most of its rain in winter.

Region	Climate type	Why
Rajasthan	Hot desert	Far from sea; rain shadow; Thar Desert
Kerala / Western Ghats	Tropical wet	First to receive SW Monsoon; 300–400 cm rain/year
Cherrapunji / Mawsynram	Wettest place on Earth	Meghalaya hills funnel Bay of Bengal branch; ~11,000 mm/year
Leh / Ladakh	Cold desert	Rain shadow behind Great Himalayas; high altitude
Tamil Nadu	Dry in SW Monsoon, wet in NE Monsoon	Lies in rain shadow during June–Sept; gets NE monsoon Oct–Dec
Mumbai	High rainfall (200+ cm)	Directly in path of Arabian Sea branch; Western Ghats behind
Delhi	Extreme continental	Away from sea; hot summers (45°C), cold winters (3°C)

75–90% of India's annual rainfall comes from SW Monsoon.
Agriculture: most crops depend entirely on monsoon — failure = drought = food crisis.
Floods: excess rain causes floods (Assam, Bihar, Kerala).
Drought: delayed or weak monsoon → crop failure → rural distress.
Economy: India's GDP growth is still closely linked to monsoon performance.
Culture: celebrated in poetry, music, festivals (Teej, Onam, Diwali follows harvest).

Term	Meaning
Monsoon	Seasonal reversal of wind direction
Orographic rainfall	Rain caused by mountains forcing moist air upward
Rain shadow	Dry area on the leeward (downwind) side of a mountain
Loo	Hot, dry summer wind blowing over north Indian plains
El Niño	Warming of Pacific Ocean surface → weakens Indian Monsoon
La Niña	Cooling of Pacific → often strengthens Indian Monsoon

Name India's four seasons with months.
Explain in four steps why the Southwest Monsoon arrives in India.
Why does Tamil Nadu receive most rain from the NE Monsoon rather than the SW Monsoon?
Why is Cherrapunji/Mawsynram the wettest place on Earth?
What is a rain shadow? Which part of India lies in the rain shadow of the Western Ghats?

Open the Practice tab for graded questions on India's Climate & Seasons.