India  Climate and the Monsoon
4 seasons, SW monsoon mechanism, branches, El Niño, climatic regions.
India  Climate and the Monsoon
Climate of India & the Monsoon
What you'll learn
- Climate vs weather — long-term averages vs day-to-day conditions.
- Factors controlling India's climate: latitude, altitude, distance from sea, wind systems.
- Four seasons of India.
- Monsoon — the most important climatic feature; its mechanism and retreat.
- El Niño and its effect on Indian monsoon.
Key concepts
Climate vs Weather
| Term | Meaning | Time scale |
|---|---|---|
| Weather | Day-to-day state of atmosphere (temp, rainfall, wind) | Hours to days |
| Climate | Average weather over 30+ years for a region | Decades |
Factors controlling India's climate
| Factor | Effect |
|---|---|
| Latitude | Southern India closer to equator → hotter; northern India has continental climate |
| Altitude | Mountains cooler (Shimla vs Delhi, same latitude) |
| Distance from sea | Coastal areas moderate temp; interiors have extreme hot/cold |
| Himalayas | Block cold Central Asian winds; force monsoon to give heavy rain |
| Western Ghats | Windward (west) side gets heavy rain; leeward (east) side — rain shadow |
| Jet streams | Fast-moving air currents in upper atmosphere influence rain patterns |
Four seasons of India
| Season | Months | Features |
|---|---|---|
| Cold Weather | Nov–Feb | Cool/cold; NE trade winds blow; North India foggy; Tamil Nadu gets rain (NE monsoon) |
| Hot Weather (Summer) | Mar–May | Very hot; dust storms; loo winds (hot dry winds in North India); temperatures 40–48°C in Rajasthan |
| South-West Monsoon (Rainy) | Jun–Sep | 75–90% of India's annual rainfall; most important season |
| Retreating Monsoon (Autumn) | Oct–Nov | Monsoon withdraws; cyclones in Bay of Bengal → Tamil Nadu & AP coast |
The South-West Monsoon — mechanism
Cause: Differential heating of land and sea.
- In summer, Indian landmass heats up rapidly → low pressure over land.
- Indian Ocean remains cooler → high pressure over sea.
- Moist winds blow from high pressure (sea) to low pressure (land) = monsoon winds.
- Moisture-laden winds rise over Western Ghats and Himalayas → cool → condense → heavy rainfall.
Two branches:
- Arabian Sea branch: hits Western Ghats first (Malabar coast, Mumbai); then crosses Deccan; reaches Central India.
- Bay of Bengal branch: hits NE India (Meghalaya, Assam) → moves west along Ganga plain.
Mawsynram (Meghalaya) — wettest place on Earth; ~11,870 mm/year; windward side of Khasi Hills.
Onset and retreat
| Event | Timing |
|---|---|
| Monsoon arrives Kerala | ~June 1 |
| Covers entire India | ~July 15 |
| Begins retreating from NW India | ~September |
| Fully withdrawn | ~December |
Break in monsoon
- Monsoon doesn't rain continuously — has wet spells and breaks (dry spells).
- During break, jet stream shifts; can last 1–3 weeks.
El Niño effect
- El Niño = unusual warming of Pacific Ocean surface waters every 2–7 years.
- Weakens Indian monsoon → drought in India.
- La Niña (cooling) → stronger monsoon → floods.
- 2002, 2009, 2014 droughts in India linked to El Niño.
Climatic regions of India (brief)
| Region | Climate type | Example |
|---|---|---|
| North-West (Rajasthan) | Hot desert / arid | Jaisalmer (<100 mm rain) |
| North India plains | Semi-arid to sub-humid | Delhi |
| North-East | Humid subtropical | Shillong, Assam |
| Western coast | Tropical monsoon | Mumbai, Kerala |
| Deccan interior | Tropical savanna | Pune, Hyderabad (rain shadow) |
| Himalayas | Alpine / mountain | Shimla, Leh |
Quick check
- What is the difference between weather and climate?
- Name four factors that control India's climate.
- What causes the South-West Monsoon to blow towards India?
- Name the two branches of the monsoon and which regions they affect first.
- What is El Niño and how does it affect India?
Open the Practice tab for graded questions on Climate.
Key Takeaways (TL;DR)
- What you'll learn
- Key concepts
- Quick check
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