Classification of Climatic Regions of India
🧭 Stamp’s Climatic Classification of India (Based on 18°C January Isotherm)
🌡️ Core Idea
Stamp used mean January temperature of 18°C to divide India into two broad climatic zones:
- Temperate (or Continental) India – North of the 18°C isotherm
- Tropical India – South of the 18°C isotherm
🗺️ The 18°C line roughly follows the Tropic of Cancer, passing through central India.
🌍 Temperate / Continental India (North of 18°C January Isotherm)
| Region | Representative City | Temperature | Rainfall | Key Features |
|---|---|---|---|---|
| Himalayan Region | Shimla (West), Darjeeling (East) | Summer: 13–18°C Winter: 4–7°C | East: >200 cm West: Less | High altitudes, snow in winter, heavy rain in East Himalayas |
| North-Western Region | Amritsar | Summer: 24°C Winter: 16°C | Below 200 cm | Moderate rainfall, continental extremes |
| Arid Lowland | – | Summer: up to 48°C Winter: 16–24°C | Below 40 cm | Desert region – Thar, Kachchh, SW Haryana |
| Region of Moderate Rainfall | Delhi | Summer: 33–35°C Winter: 15–18°C | 40–80 cm | Semi-arid belt – Punjab, Haryana, west UP, Delhi |
| Transitional Zone | Patna | Summer: 30–35°C Winter: 15–19°C | 100–150 cm | Transitional between dry and moist – Bihar, east UP |
🌴 Tropical India (South of 18°C January Isotherm)
| Region | Representative City | Temperature | Rainfall | Key Features |
|---|---|---|---|---|
| Very Heavy Rainfall Region | Cherrapunji | Summer: 32–35°C Winter: 18°C | >200 cm Mawsynram: 1221 cm | NE states – wettest place on Earth |
| Heavy Rainfall Region | Kolkata | Summer: 29–35°C Winter: 18–24°C | 100–200 cm | East coast – rain from Bay of Bengal branch |
| Moderate Rainfall Region | Hyderabad | Summer: 32°C Winter: 18–24°C | 50–100 cm | Rain shadow of Western Ghats |
| Konkan Coast | Mumbai | Annual: 24–27°C | >200 cm | Narrow coastal belt – receives SW monsoon showers |
| Malabar Coast | Thiruvananthapuram | Annual: 27°C | >250 cm | High rainfall due to Western Ghats and monsoons |
| Tamil Nadu Region | Chennai | Annual: 24°C | 100–150 cm | Gets rain from Retreating Monsoon (Oct-Nov) |
🧠 How to Remember It Better?
- Divide by the 18°C January Isotherm (Temperate north, Tropical south).
- Temperate = Himalayas to Delhi belt; includes deserts, plains, and plateaus.
- Tropical = NE India + Southern Peninsular India.
- Focus on rainfall pattern:
- East = Bay of Bengal
- West = Arabian Sea
- Interior = Rain shadow
- Tamil Nadu = Retreating Monsoon
🌎 Koeppen’s Climatic Classification of India
Please revisit Koeppen’s climatic Classification in Climatology section before reading this topic.
🧭 Koeppen’s Climatic Regions in India
| Code | Climate Type | Region | Rainfall | Notes |
|---|---|---|---|---|
| Amw | Tropical monsoon with short dry winter | Western coast south of Mumbai | > 300 cm | Heavy SW monsoon rain, short dry season |
| As | Monsoon with dry summer (high sun dry) | Coromandel Coast (Tamil Nadu & S. Andhra) | 75–100 cm | Dry summer, wet winter (retreating monsoon) |
| Aw | Tropical savannah | Most of peninsular plateau | ~75 cm | Winter dry; typical tropical climate |
| BShw | Semi-arid steppe | Rain-shadow of Western Ghats, parts of Rajasthan, Gujarat, Haryana | 12–25 cm | Semi-desert; short monsoon |
| BWhw | Hot desert | Thar Desert (W Rajasthan) | < 12 cm | True desert conditions |
| Cwg | Monsoon with dry winter (warm temperate) | Ganga plain, eastern Rajasthan, Malwa, Assam | 100–200 cm | Typical North Indian monsoon |
| Dfc | Cold, humid with short summer | Sikkim, Arunachal Pradesh, N Assam | ~200 cm | Snowfall in winter, cold climate |
| Et | Tundra type | Higher Himalayas (e.g. Uttarakhand hills) | Varies | Avg. temp: 0–10°C, seasonal snow |
| E | Polar type | J&K, Himachal High Altitudes | Snowfall | Warmest month: <10°C |
