Climate of India
Introduction
'India's climate is described as a MONSOON TYPE of climate — found mainly in South and Southeast Asia. The word MONSOON comes from the Arabic word "MAUSIM" (season). The climate is CHARACTERISED by a REVERSAL of winds between summer and winter. ICSE examiners ALWAYS ask: "Why does India have a MONSOON climate?" and "How do the monsoon winds BRING rainfall to different parts of India?"'
Factors Affecting India's Climate
1. Latitude
- The Tropic of Cancer (23°30'N) passes through the MIDDLE of India
- Southern India (near equator) is HOTTER and has LESS seasonal variation
- Northern India has MORE extreme temperatures (hot summers, cold winters)
2. The Himalayas
| Function | Explanation |
|---|
| Barrier to COLD winds | BLOCK the freezing polar winds from Central Asia — India is WARMER than other regions at the SAME latitude |
| Trap MONSOON winds | FORCE the moisture-laden monsoon winds to RISE and COOL — causing HEAVY rainfall |
3. Altitude
- Temperature DECREASES with altitude
- Example: Ooty (2,240 m) is COOL while Chennai (sea level) is HOT
4. Distance from the Sea (Continentality)
- COASTAL areas have EQUABLE climate (moderate — no extremes)
- INLAND areas have EXTREME climate (hot summers, cold winters)
5. Pressure and Winds
| Season | Pressure | Winds |
|---|
| SUMMER | LOW pressure over NORTH India | Winds blow from HIGH pressure (Indian Ocean) TOWARDS land |
| WINTER | HIGH pressure over NORTH India | Winds blow from HIGH pressure (land) TOWARDS sea |
6. Ocean Currents
- EL NINO affects the MONSOON — WARM currents in the Pacific weaken Indian monsoon
- La Nina STRENGTHENS the monsoon
7. Jet Streams
- TROPICAL EASTERLY JET STREAM (TEJ) — helps BRING monsoon winds
- SUBTROPICAL WESTERLY JET STREAM — brings WINTER rainfall to northwest India
The Monsoon Mechanism
What is a Monsoon?
'Monsoon = SEASONAL reversal of winds. In summer, winds blow from SEA to LAND (bringing rain). In winter, winds blow from LAND to SEA.'
The Southwest Monsoon (June–September)
| Step | Process |
|---|
| 1 | INTENSE heating of the Thar Desert and North India in summer |
| 2 | LOW pressure area forms over NORTH India |
| 3 | MOISTURE-LADEN winds from the Indian Ocean rush toward this LOW pressure |
| 4 | Winds are DEFLECTED by the Coriolis force — they approach India from the SOUTHWEST |
| 5 | The WESTERN GHATS block the winds — causing HEAVY rainfall on the WINDWARD side |
| 6 | The RAIN-SHADOW area (east of Ghats, like Bangalore) gets LESS rain |
| 7 | The BAY OF BENGAL branch moves toward the HIMALAYAS — cause HEAVY rain in NE India |
Two Branches of SW Monsoon
| Branch | Path | Rainfall |
|---|
| ARABIAN SEA Branch | Western Ghats -> Mumbai -> Gujarat -> Punjab | HEAVY on west coast. LESS beyond Ghats |
| BAY OF BENGAL Branch | Myanmar -> Northeast India -> Ganga Plain -> Punjab | VERY HEAVY in NE India (Mawsynram, Cherrapunji) |
ICSE Focus: Windward vs Leeward
| Side | Location | Rainfall | Reason |
|---|
| WINDWARD | Western side of Western Ghats | HEAVY (200–400 cm) | Winds RISE and COOL |
| LEEWARD | Eastern side of Western Ghats | LOW (60–80 cm) | Winds DESCEND and WARM |
The Northeast Monsoon (October–November)
| Aspect | Detail |
|---|
| Direction | Winds blow from NORTH-EAST (land to sea) — usually DRY |
| Rain | Brings SOME rain to Tamil Nadu coast (Coromandel) — because they pick up MOISTURE from the Bay of Bengal |
| ICSE Note | 'Tamil Nadu gets MOST of its rainfall from the NORTH-EAST monsoon — THIS is a common exam question.' |
Seasons of India
| Season | Months | Characteristics |
|---|
| COLD Weather | December–February | Clear skies, COOL temperatures. Northwest India: 10–15°C. South India: 20–25°C |
| HOT Weather | March–May | TEMPERATURES rise. 45°C in Rajasthan. LOOs (hot dry winds). Pre-monsoon showers |
| SOUTHWEST MONSOON | June–September | RAINY season. 75% of India's ANNUAL rainfall |
| RETREATING MONSOON | October–November | Winds REVERSE. Tropical CYCLONES form in the Bay of Bengal |
Distribution of Rainfall
| Category | Rainfall (cm) | Areas |
|---|
| VERY HIGH | 200+ | W. Ghats, NE India, Meghalaya, Andaman Islands |
| HIGH | 100–200 | Ganga Plain, Odisha, Chhattisgarh |
| MODERATE | 50–100 | Deccan Plateau, Gujarat, Rajasthan |
| LOW | 25–50 | Punjab, Haryana, Kutch |
| SCANTY | < 25 | THAR DESERT (Far-Western Rajasthan), Rann of Kutch |
Mawsynram (Meghalaya)
- WETTEST place in India — average 1,187 cm ANNUALLY
- Receives rain from BOTH the Bay of Bengal AND Arabian Sea branches
Tropical Cyclones
| Aspect | Detail |
|---|
| Season | OCTOBER–DECEMBER (post-monsoon) |
| Origin | Bay of Bengal (more) and Arabian Sea |
| Formation | Warm SEA temperatures + high HUMIDITY |
| Impact | HEAVY rainfall, floods, storm surges — ESPECIALLY in Odisha, Andhra, West Bengal |
| Example | Cyclone AMPHAN (2020), Cyclone FANI (2019) |
Common Mistakes in ICSE Answers
| Mistake | Correction |
|---|
| Confusing WINDWARD and LEEWARD | Windward = gets MORE rain (faces the wind) |
| Forgetting TAMIL NADU gets rain from NORTH-EAST monsoon | This is the EXCEPTION — exams test it |
| Ignoring the JET STREAMS | TEJ (Tropical Easterly Jet) drives the monsoon |
| Calling India's climate 'tropical' | It is MONSOON type — not purely tropical |
ICSE Exam Focus — Marks Blueprint
| Question Type | Marks | Frequency |
|---|
| Factors affecting India's climate | 6-8 | Always |
| Mechanism of the SOUTHWEST monsoon | 6-8 | Always |
| Distribution of rainfall | 4-6 | Very High |
| Windward vs Leeward side | 4-5 | Very High |
| Seasons of India | 4-6 | High |
Self-Test
-
Monsoon: What is a MONSOON? Explain how the SOUTHWEST MONSOON brings rainfall to India.
-
Factors: State ANY FOUR factors that affect India's climate. How does the HIMALAYAS influence climate?
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Rainfall: On the Western Ghats, which side gets MORE rainfall? Why? What is the RAIN-SHADOW region?
-
Tamil Nadu: Why does Tamil Nadu receive rainfall in WINTER (Oct–Dec)? Which monsoon brings this rain?
-
Seasons: Name the FOUR seasons of India. Which season receives 75% of India's annual rainfall?
-
Cyclones: When do tropical CYCLONES affect India? Which coast is more affected — East or West?
-
Jet Streams: How do JET STREAMS influence the Indian monsoon? Explain the role of the TROPICAL EASTERLY JET STREAM.
