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Revision: Contemporary India - 1 >> Climate Social Science English Medium Class 9 CBSE

Season: A season is a period of the year that is distinguished by special climate conditions.

Key Points: Climate of India

India lies between 8°4′N and 37°6′N, giving it both tropical and temperate climates.
It has a tropical monsoon climate with high temperatures and seasonal rainfall.
The Tropic of Cancer divides India into southern tropical and northern temperate zones.
The Himalayas block cold winds, and the Indian Ocean provides moisture for monsoon rains.
In summer, south-west monsoon winds bring heavy rain to coastal and mountain areas.
North-east monsoon winds bring some rain to the south during the retreating monsoon.
India's diverse geography causes regional climate differences and natural disasters like floods, droughts, and cyclones.

Key Points: Factors Affecting India's Climate

Latitude – Southern India is warmer as it lies in the tropical zone; northern India lies in the temperate zone.
Altitude – Temperature decreases with height; hills are cooler than plains.
Distance from Sea – Coastal areas have moderate climate; interior areas have extreme climate.
Himalayas – Block cold winds and cause rainfall by stopping monsoon winds.
Monsoon & El Niño – Monsoon controls rainfall; El Niño weakens monsoon, La Niña strengthens it.

Key Points: Seasons in India > Hot Dry Summer

Hot dry summer season lasts from March to May due to the sun’s vertical rays moving towards the Tropic of Cancer.
High temperatures occur in interior India, while coastal and hilly areas are cooler.
Low pressure develops over north and northwest India; seas have high pressure.
Local winds like Loo and Kalbaisakhi blow during this season.
Pre-monsoon showers (Mango/Blossom showers) help crops like tea, coffee, rice, and mango.

Key Points: Seasons in India > The South-West Monsoon Season

South-West Monsoon season lasts from June to September and is the main rainy season of India.
It is caused by differential heating of land and sea, creating low pressure over north-west India and high pressure over surrounding seas.
South-East Trade Winds, after crossing the Equator, are deflected by the Coriolis force and blow as South-West Monsoon winds.
These winds divide into two branches due to India’s peninsular shape: Arabian Sea branch and Bay of Bengal branch.
The monsoon brings heavy, uneven rainfall, with orographic rain on windward slopes, while Tamil Nadu and western Rajasthan receive little rainfall.

Key Points: Seasons in India > Retreating Monsoon

Retreating Monsoon season occurs during October and November due to the weakening of the low-pressure trough over the Ganga plains.
The retreat of monsoon is caused by the southward movement of the sun, leading to high pressure replacing low pressure over northern India.
Clear skies, high humidity, and high temperature cause uncomfortable weather called ‘October Heat’.
Cyclonic depressions form over the Bay of Bengal and Andaman Sea, bringing heavy rainfall to Tamil Nadu, Odisha, and coastal Karnataka.
Interior Deccan remains dry due to the rain-shadow effect of the Eastern Ghats, while the Coromandel Coast receives most of its rainfall.

Key Points: Distribution of Rainfall

Distribution of rainfall in India depends on pressure conditions, relief features, wind direction, and cyclonic depressions.
Heavy rainfall regions (more than 200 cm) include the windward slopes of the Western Ghats and the Meghalaya–Assam hills.
Moderate rainfall regions (100–200 cm) include the Middle Ganga Valley, parts of Odisha, Madhya Pradesh, Maharashtra, Andhra Pradesh, and Tamil Nadu.
Low rainfall regions (50–100 cm) include parts of the Deccan Plateau, Punjab, Haryana, eastern Rajasthan, and Kashmir.
Scanty rainfall regions (less than 50 cm) include the Thar Desert, Kachchh, and rain-shadow areas of the Deccan Plateau, making rainfall in India uneven and uncertain.