The temperature and rainfall from the bases of this classification. 18°C winter isotherm divides India into Continental and Tropical regions and further sub-divisions are according to amount of rainfall.
(1) Continental India:
(i) Himalayan Region
(ii) NW Plateau
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(iii) NW dry Plains
(iv) Region of Moderate rains
(v) Transitional Zone of high and medium rains.
(2) Tropical India:
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(i) Region of very high rain fall
(ii) Region of high rainfall
(iii) Region of moderate rainfall
(iv) Konkan Coast
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(v) Malbar Coast
(vi) Tamil Nadu Coast.
(i) Himalayan Region.
Itextends in the north and NE part of India. Altitude is the decisive factor and determinant of cause and amount of rainfall. Mean summer temperature ranges between 13-18°C and mean winter temperature 4°-7°C.
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Rainfall decreases towards the west. It is 125 cm in the west, 150 cm in the middle and over 200 cm in the east. Snowfall occurs during winter.
(ii) NW Plateau.
To the north-west of Sutlej mean summer temperature is 34°C and mean winter temperature remains 16°C. Average rainfall is less, nearly 40 cm, caused by winter cyclones.
(iii) NW dries Plains.
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SW Haryana, Punjab and Rajasthan. Mean summer temperature 46°C
Mean winter temperature 13-24°C Average annual rainfall less than 50 cm
(iv) Region of moderate Rains.
Western UP, Punjab, Haryana, Eastern Rajasthan and Delhi.
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Mean summer temperature 35°C
Mean winter temperature 15°-18°C
A high annual range of temperature rainfall 40-80 cm
Summers are partially dry but rain comes in winters due to winter cyclones.
(v) Transitional Zone.
N. Bihar and eastern UP Summer mean: 35°C
Winter mean: 16-18°C
Rainfall by S.W Monsoons: 100-150 cm.
(vi) Region of high Rainfall.
Middle lower Ganga valley Mean summer temperature: 29-35°C Mean winter temperature: 18-24°C
Mean rainfall 100-200 cm. less towards the west and southwards.
(vii) Region of very high Rainfall.
All the North-Eastern States. It is a region of humid climate. Rainy season is long. Average annual rainfall is over 250 cm.
(viii) Region of moderate Rainfall.
Gujarat, Southern M.E, Karnataka and Western A.P Average annual rainfall is 75 cm due to rain shadow effect.
Mean summer temperature: 32°C
Mean winter temperature: 18-24°C
(ix) Konkan Coast.
From Narmada Estuary to Goa annual range of temperature is very less i.e. 3°C. Average annual rainfall exceeds 200 cm and is caused by the SW Monsoon.
(x) Malabar Coast.
Goa-Kanyakumari region gets heavy rainfall exceeding 500 cm a year. SW Monsoons bring rainfall. Annual range of temperature is low; nearly 3°C.
(xi) Tamil Nadu Coast.
Annual range of temperature is 3°C. Rainfall 100-150 cm and it is due to retreating monsoons.