Maarg Manthan · Topic 16.4

Climatic Regions of India

Geography › Indian Monsoon, Climate, Vegetation and Soils · Topic 16.4

Climatic regions of India are classified mainly by rainfall, since rainfall varies more than temperature. Stamp divided the country along the 18 degree January isotherm into a temperate or continental zone and a tropical zone, and then into eleven regions. Köppen used temperature, rainfall and vegetation to name types such as Amw, Aw, BWhw and Cwg. Rainfall zones are heavy, moderate, low and arid.

5 min read · UPSC Prelims · Geography · Indian Monsoon, Climate, Vegetation and Soils

At a Glance

Stamp 18 degrees January isotherm; eleven regions
Köppen Nine types: Amw, As, Aw, BShw, BWhw, Cwg, Dfc, ET, E
Wettest region Meghalaya, Assam hills, Western Ghats windward slopes
Driest region West Rajasthan, Kachchh
Transition Eastern Uttar Pradesh and Bihar
Exam link UPSC Prelims, Geography: Indian Monsoon, Climate, Vegetation and Soils

Where Does It Fit?

This is the fourth topic of the macro on the Indian monsoon, climate, vegetation and soils. The previous topic followed the year through the seasons, and this one divides the country into regions of similar climate. The next topic describes the natural vegetation that these climates produce. Previous topic: Seasons of India. Next topic: Natural Vegetation of India.

What Are Stamp’s Climatic Regions?

In short: Stamp splits India into a northern temperate half and a southern tropical half, then into regions by rainfall.

L. Dudley Stamp used the January mean temperature of 18 degrees Celsius to divide India into the temperate or continental zone in the north and the tropical zone in the south. The line runs roughly across the base of the Peninsula along the Tropic of Cancer. Each zone was divided into regions by rainfall and temperature.

Zone	Region	Area and features
Temperate or continental	Himalayan region	Heavy rain in the east, over 200 cm, and much less in the west; cold winters, cool summers
Temperate or continental	North-western region	Northern Punjab and southern Jammu and Kashmir; below 40 cm to 80 cm of rain; hot summers, cold winters
Temperate or continental	Arid lowland	Thar desert, south-west Haryana and Kachchh; under 40 cm; summers of about 48 degrees
Temperate or continental	Region of moderate rainfall	Punjab, Haryana, west Uttar Pradesh, Delhi, eastern Rajasthan and parts of Madhya Pradesh; 40 to 80 cm
Temperate or continental	Transitional zone	Eastern Uttar Pradesh and Bihar; 100 to 150 cm
Tropical	Very heavy rainfall	Meghalaya, Assam, Tripura, Mizoram and Nagaland; over 250 cm
Tropical	Heavy rainfall	Chhattisgarh, Jharkhand, Gangetic West Bengal, Odisha and coastal Andhra Pradesh; 100 to 200 cm
Tropical	Moderate rainfall	Plateau between the Western and Eastern Ghats; 50 to 100 cm
Tropical	Konkan coast	Mumbai to Goa; heavy summer rain; annual temperature about 24 to 27 degrees
Tropical	Malabar coast	Goa to Kanyakumari; heavy rain; about 27 degrees
Tropical	Tamil Nadu	Rain mainly in October to December from the northeast monsoon, with about 100 to 150 cm

What Are Köppen’s Climatic Types in India?

Code	Type	Region
Amw	Monsoon type with a short dry winter	West coast south of Mumbai; over 300 cm
As	Monsoon type with a dry season in the high-sun period	Coromandel coast of Tamil Nadu and neighbouring Andhra Pradesh
Aw	Tropical savanna	Most of the peninsular plateau except the coastal strips
BShw	Semi-arid steppe	Rain-shadow areas of the Ghats, much of Rajasthan, Haryana and Gujarat
BWhw	Hot desert	Most of western Rajasthan; under 25 cm
Cwg	Monsoon type with dry winters	Most of the Ganga plain, eastern Rajasthan, Assam and the Malwa plateau; the g refers to the Gangetic type, in which the hottest month comes before the solstice
Dfc	Cold, humid winters with a short summer	Sikkim, Arunachal Pradesh and parts of Assam
ET	Tundra	High mountains of Uttarakhand
E	Polar type	Higher parts of Jammu and Kashmir, Himachal Pradesh and Ladakh; snow

The codes follow the Köppen system, as in Köppen Scheme of Climate Classification, and the types of Group A are described in Tropical Humid Climates (Group A).

What Are the Rainfall Zones and What Do They Mean for Land Use?

Heavy rainfall (over 200 cm): the windward Western Ghats, the north-eastern hills, parts of the Himalaya, the Brahmaputra valley and the sub-Himalayan West Bengal; evergreen forest, tea, rubber and rice.
Moderate rainfall (100 to 200 cm): southern Gujarat, east Tamil Nadu, north-eastern Peninsula, the Ganga plain; deciduous forest, rice, sugarcane, jute.
Low rainfall (50 to 100 cm): Uttar Pradesh west, Rajasthan east, the Deccan interior; millets, pulses, cotton, wheat with irrigation.
Arid (below 50 cm): Gujarat, Rajasthan, Haryana and Punjab parts, the rain-shadow strip of Karnataka and Maharashtra; desert and thorn scrub, as in Dry and Warm Temperate Climates (Groups B and C).

India Meteorological Department also divides the country into homogeneous rainfall regions for forecasting: North-West India, Central India, South Peninsula, and East and North-East India, which is the basis of the regional figures in the seasonal reports. As an analytical point, the regional pattern shows that rainfall, and not temperature, is the key line of division in India, and so farming systems, forest types and water policy are all organised along the rainfall isohyets: the 100 cm line separates rice from wheat and millets, and the 50 cm line the limit of rain-fed farming. A warming climate is expected to shift these lines and increase the weight of extremes, in particular in the western Himalaya and the dry lands.

Why Is This Topic Important?

Core topic Stamp and Köppen asked
Link Vegetation and crops
Application Planning by region

What Came Next?

The next topic describes the natural vegetation of India. Next topic: Natural Vegetation of India.

Key People and Terms

Stamp Geographer who classified Indian climates
Isohyet Line of equal rainfall
Amw Western coast monsoon climate
Aw Savanna of the plateau
Cwg Ganga plain climate
Homogeneous region IMD forecast region

Exam Corner

Points to Remember

Stamp used the 18 degree January isotherm.
Stamp gave eleven regions; Köppen nine.
Aw covers most of the plateau.
Cwg is the Ganga plain.
BWhw is west Rajasthan.

Do Not Confuse With

Amw and As Heavy west coast versus dry-summer east coast
Aw and Cwg Plateau savanna versus Ganga plain
Stamp and Köppen Rainfall-based regions versus code-based types

Memory Hook

Stamp splits at 18 degrees, rainfall decides the rest; Köppen’s codes: Amw west, Aw plateau, Cwg plain, BWhw desert.

Mains Angle

Questions ask to match regions with climate types. These points add depth.

Basis Rainfall over temperature
Types Köppen mapping
Use Crops and forests

A Question You May Face

An original practice question, not a past paper question.

“Describe the climatic regions of India according to Köppen and explain how rainfall determines the pattern of vegetation and cropping.”

How to Answer

Basis Rainfall and temperature.
Stamp Two zones, eleven regions.
Köppen Nine types.
Link Vegetation and crops.

GS Relevance

Prelims: Stamp and Köppen regions, rainfall zones, which codes apply where. GS Paper 1: regional climate of India and its link to vegetation and agriculture.

Frequently Asked Questions

How did Stamp classify the climatic regions of India?

L. Dudley Stamp used the January mean temperature of 18 degrees Celsius to divide India into a temperate or continental northern zone and a tropical southern zone. He further divided them into eleven regions using rainfall and temperature, from the Himalayan region to the Malabar coast and Tamil Nadu.

What are the Köppen climatic types of India?

Köppen's types in India are Amw on the western coast, As on the Coromandel coast, Aw over most of the peninsular plateau, BShw in semi-arid areas, BWhw in the hot desert of Rajasthan, Cwg over the Ganga plain, Dfc in Sikkim and Arunachal, and ET and E in the high mountains.

Which climatic type covers most of the Peninsular Plateau?

The Aw type, the tropical savanna climate, covers most of the Peninsular Plateau except for the coastal strips. It has a dry winter and a rainy summer, and its natural vegetation consists of deciduous forest and savanna woodland.

What does the g in Cwg mean?

In the Köppen code Cwg, the letter g indicates the Gangetic type of temperature pattern, in which the hottest month occurs before the summer solstice and the monsoon rains, not after it. The Cw part refers to a warm temperate climate with a dry winter, which describes much of the Ganga plain.

Why is rainfall more important than temperature in classifying Indian climates?

Rainfall in India varies much more across the country, from under 10 centimetres in parts of the Thar to over 1,000 centimetres at Mawsynram, than temperature does. Rainfall decides vegetation, crops and water supply, so geographers classify Indian climates mainly by the amount and timing of rain.

PYQ Practice — Statement Analysis

1 Stamp used the 18 degree Celsius January isotherm to divide India.

True

It separates temperate and tropical zones.

2 Most of the peninsular plateau has an Aw climate.