Geography
Indian Climate and the Monsoon
GS Paper I
Indian Climate and the Monsoon — Quick Revision
One-page UPSC revision of Indian climate: monsoon mechanism, IMD normal dates, ENSO and IOD, the four seasons, local winds, rainfall pattern and Köppen regions.
SyllabusGS I · Salient features of world's physical geography; physical geography of India — climate, monsoon and important geophysical phenomena
A last-week revision sheet for Indian climate. Prelims tests the mechanism, the exceptions and the local names.
The Mechanism in One Table
| Driver | Role |
|---|---|
| Differential heating | Low over the land, high over the seas in summer |
| ITCZ shift | Settles over the Ganga plain as the monsoon trough |
| Mascarene High | High pressure east of Madagascar; drives cross-equatorial flow |
| Tibetan plateau | Intense summer heating; rising air shapes upper-air circulation |
| Westerly jet | South of the Himalayas in winter; moves north in summer |
| Tropical Easterly Jet | Over the Peninsula in summer |
| ENSO / IOD | Year-to-year variability |
Dates and Numbers (IMD)
| Item | Value |
|---|---|
| Onset over Kerala | 1 June |
| Covers the country | 8 July (revised 2020) |
| Withdrawal begins (north-west India) | 17 September (revised 2020) |
| Withdrawal complete | 15 October |
| LPA (1971–2020) | 87 cm |
| Normal season | 96–104% of LPA |
Seasons and Local Weather
| Season | Months | Key feature |
|---|---|---|
| Cold weather | Dec–Feb | Western disturbances (north-west); north-east monsoon (Tamil Nadu) |
| Hot weather | Mar–May | Loo; mango showers; blossom showers; Kalbaisakhi |
| South-west monsoon | Jun–Sep | Arabian Sea and Bay of Bengal branches; breaks |
| Retreating monsoon | Oct–Nov | October heat; Bay of Bengal cyclones; Tamil Nadu rain |
ENSO and IOD
| Condition | Tendency for Indian monsoon |
|---|---|
| El Niño | Weaker |
| La Niña | Stronger |
| Positive IOD (west Indian Ocean warmer) | Stronger |
| Negative IOD (east Indian Ocean warmer) | Weaker |
Köppen Regions (selected)
| Code | Where |
|---|---|
| Amw | West coast south of Goa |
| As | Coromandel coast |
| Aw | Most of the Peninsular plateau |
| BWhw | Extreme western Rajasthan |
| Cwg | Ganga plain |
High-yield facts
- Tamil Nadu coast: dry in June–September (parallel to the Bay branch; rain shadow of the Arabian Sea branch); wet in October–December.
- Mawsynram and Cherrapunji — funnel effect of the Khasi hills on the Bay of Bengal branch.
- A break in the monsoon occurs when the monsoon trough shifts to the Himalayan foothills.
- Kalbaisakhi in Assam: “Bardoli Chheerha”.
Common Traps
Watch for these
- El Niño raises the risk of a weak monsoon; it does not guarantee drought.
- The westerly jet is south of the Himalayas in winter, north in summer.
- Western disturbances bring winter rain to the north-west, not to the south.
Related Topics
- Mechanism of the Indian Monsoon
- Indian Climate and the Monsoon — practice questions
- Climatology
- All quick revision sheets
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