NCERT Class 9 Geography Chapter 4 – Climate

These NCERT Class 9 Geography Chapter 4 notes explain the climatic system of India, especially the Tropical Monsoon Climate that defines seasonal changes across the country. The chapter builds conceptual clarity about the mechanism of monsoon and factors influencing India’s weather patterns.

India’s climate is influenced by multiple factors such as Latitude (Tropic of Cancer – 23°30′ N), Altitude, Pressure and Wind Systems, Distance from the Sea (Continentality), Ocean Currents, and Relief features like the Himalayas and Western Ghats.

The chapter explains global climatic influences such as the Inter Tropical Convergence Zone (ITCZ), Subtropical Westerly Jet Stream, Tropical Easterly Jet Stream, and the El Niño–Southern Oscillation (ENSO) phenomenon.

• It also describes the four major seasons of India:
• Cold Weather Season (December–February),
• Hot Weather Season (March–May),
• Advancing Monsoon Season (June–September), and
• Retreating Monsoon Season (October–November).

Important climatic data such as 118 cm average annual rainfall, onset of monsoon over Kerala (around 1st June), heavy rainfall in Mawsynram and Cherrapunji, and low rainfall in Thar Desert and Ladakh (less than 25 cm) are explained clearly.

These notes strictly follow the NCERT textbook Contemporary India – I and are highly useful for CBSE exams, state board exams and BPSC foundation preparation.

For structured preparation of NCERT Class 9–12 for UPSC, BPSC and State PCS examinations, strengthen your basics with our complete NCERT Book Notes PDF for Class 9-12, available inside the NCERT foundation course level-2.

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1. Climate of India

• Climate refers to the average weather conditions over a long period (generally 30 years or more) for a large area.
• India has a Tropical Monsoon Climate, characterized by seasonal reversal of winds, distinct wet and dry seasons, and uneven distribution of rainfall.
• Despite regional variations, the Indian climate shows a broad unity due to the dominant influence of the Monsoon winds.
• India’s climate is strongly influenced by the presence of the Himalayas in the north and the Indian Ocean in the south.
• The climatic pattern directly affects agriculture, economy, vegetation, river flow, and population distribution.

2. Factors affecting the climate of India

• Latitude – The Tropic of Cancer (23°30′ N) passes almost through the middle of India, dividing it into tropical (south) and subtropical (north) regions.
• Altitude – Temperature decreases with height at an average rate of 1°C for every 165 metres; hence Shimla, Ooty, Darjeeling are cooler than plains.
• Pressure and wind system – Seasonal formation of low pressure over Northwest India in summer and high pressure in winter causes wind reversal.
• Distance from the sea (Continentality) – Coastal cities like Mumbai and Chennai have moderate climate, whereas Delhi and Amritsar experience extreme temperatures.
• Ocean currents – Warm ocean currents in the Arabian Sea and Bay of Bengal influence coastal temperatures.
• Relief features – The Western Ghats cause heavy rainfall on the windward side and create rain shadow areas like Pune and Bengaluru.

3. Global climatic influences on Indian monsoon

• The Inter Tropical Convergence Zone (ITCZ) shifts northwards over the Ganga Plain in July, bringing monsoon rainfall.
• The Subtropical Westerly Jet Stream blows south of the Himalayas in winter, bringing Western Disturbances and rainfall to Punjab and Haryana.
• In summer, the Tropical Easterly Jet Stream develops over the peninsula, strengthening the Southwest Monsoon.
• The Tibetan Plateau heats up intensely during summer, creating a strong low-pressure system that attracts monsoon winds.
• The Southern Oscillation refers to periodic changes in air pressure over the Indian Ocean and Pacific Ocean.
• El Niño (warming of Pacific Ocean waters) weakens Indian monsoon; strong El Niño years often lead to drought conditions in India.

4. The mechanism of monsoon

• During summer, intense heating of landmass creates low pressure over Northwest India, while the Indian Ocean remains comparatively cooler.
• The southeast trade winds cross the equator, get deflected due to the Coriolis force, and become the Southwest Monsoon Winds.
• These winds split into two branches: the Arabian Sea Branch and the Bay of Bengal Branch.
• The Arabian Sea Branch strikes the Western Ghats, causing heavy rainfall in Konkan, Goa, and Malabar Coast.
• The Bay of Bengal Branch moves towards Assam and Meghalaya, bringing heavy rainfall in Mawsynram and Cherrapunji.
• The phenomenon of ‘Burst of Monsoon’ refers to the sudden heavy rainfall at the onset of monsoon.

5. The four seasons of India

• India experiences four distinct seasons: Cold Weather Season (Winter), Hot Weather Season (Summer), Advancing Monsoon Season, and Retreating Monsoon Season.
• Seasonal variation is mainly due to the apparent movement of the Sun between the Tropic of Cancer and Tropic of Capricorn.
• Each season has distinct temperature, pressure and wind conditions.

6. Cold weather season (December–February)

• During winter, the sun is overhead at the Tropic of Capricorn, resulting in cooler conditions in northern India.
• Average temperatures range from 10°–15°C in Northern Plains, while southern regions remain around 20°–25°C.
• Frost and fog are common in North India during this season.
• Western Disturbances bring light rainfall to Punjab, Haryana, Delhi, Western Uttar Pradesh, beneficial for Rabi crops.
• Northeast trade winds blow from land to sea and are generally dry except over Tamil Nadu coast, which receives some rainfall.

7. Hot weather season (March–May)

• Temperatures rise sharply, reaching 45°C in Rajasthan, Madhya Pradesh, and Uttar Pradesh.
• A hot and dry wind called Loo blows across northern plains during May and June.
• Dust storms are common in Punjab, Haryana and Rajasthan.
• Pre-monsoon showers called ‘Mango Showers’ occur in Kerala and Karnataka.
• Local storms known as ‘Kal Baisakhi’ (Nor’westers) occur in West Bengal and Assam, helpful for tea cultivation.

8. Advancing monsoon season (June–September)

• The Southwest Monsoon sets in over Kerala around 1st June and covers the entire country by mid-July.
• Nearly 75% of India’s total annual rainfall occurs during this period.
• Average annual rainfall of India is about 118 cm.
• Rainfall decreases from East to West in Northern Plains, with Kolkata receiving more rainfall than Delhi.
• Mawsynram (Meghalaya) records the highest average rainfall in the world (above 1,000 cm annually).
• Breaks in monsoon occur due to shifting of the Monsoon Trough, causing dry spells in some regions.

9. Retreating monsoon season (October–November)

• Also called the Northeast Monsoon Season.
• Withdrawal of monsoon begins from Northwest India in September and retreats completely by early December.
• The day temperature remains high while nights become cooler, creating ‘October Heat’ conditions.
• The Tamil Nadu coast receives heavy rainfall during this period from Northeast Trade Winds.
• Tropical cyclones frequently develop in the Bay of Bengal, affecting Odisha, Andhra Pradesh and Tamil Nadu.

10. Distribution and variability of rainfall

• Heavy rainfall occurs along the Western Ghats and Northeastern states.
• Moderate rainfall occurs in the Northern Plains and eastern coastal regions.
• Low rainfall (less than 25 cm annually) occurs in the Thar Desert (Rajasthan) and Ladakh region.
• Rainfall is uneven and unpredictable, leading to floods in Assam and Bihar and droughts in Rajasthan.
• India’s agriculture is largely dependent on the timely arrival and proper distribution of monsoon rainfall.

11. Monsoon as a unifying bond

• The monsoon influences the entire country from agriculture to economy.
• Crops like Rice, Cotton, Jute and Sugarcane depend heavily on monsoon rains.
• The rhythm of Indian life, including festivals and farming cycles, revolves around the monsoon.
• Variability in monsoon affects GDP growth, food production and rural livelihood.

12. Conclusion

• India’s climate is shaped by complex interactions of latitude, pressure systems, jet streams, Tibetan Plateau heating and oceanic phenomena.
• The Monsoon system remains the backbone of India’s climatic identity.
• Seasonal reversal of winds gives India a distinct climatic character compared to other tropical countries.
• Effective climate management and disaster preparedness are crucial due to increasing climate variability and extreme events.

13. Important Exam Oriented Facts

• 23°30′ N (Tropic of Cancer) – Divides India into tropical and subtropical zones.
• ITCZ – Inter Tropical Convergence Zone shifting northward in July.
• Subtropical Westerly Jet Stream – Causes Western Disturbances in winter.
• Tropical Easterly Jet Stream – Develops in summer and strengthens monsoon.
• El Niño – Weakens Indian monsoon; linked to drought years.
• 1st June – Onset of Southwest Monsoon over Kerala.
• 75% rainfall – Received during June–September.
• 118 cm – Average annual rainfall of India.
• Mawsynram – Wettest place on Earth.
• Thar Desert & Ladakh – Receive less than 25 cm rainfall annually.
• Loo – Hot wind of North India.
• Kal Baisakhi – Pre-monsoon storms in West Bengal.
• Mango Showers – Pre-monsoon showers in Kerala.
• October Heat – High day temperatures during retreating monsoon.
• Western Disturbances – Winter rainfall system from Mediterranean region.

Understanding NCERT Class 9 Geography Chapter 4 – Climate is essential to analyse how monsoon winds influence agriculture, economy and daily life in India.

The chapter clearly explains the mechanism of Southwest Monsoon, including the role of Tibetan Plateau heating, low-pressure formation over Northwest India, and the two branches of monsoon — Arabian Sea Branch and Bay of Bengal Branch.

For school examinations, students must focus on key terms such as Loo (hot wind), Kal Baisakhi (Nor’westers), Mango Showers, Western Disturbances, October Heat, and rainfall distribution patterns.

For BPSC and civil services foundation studies, this chapter provides analytical understanding of climate variability, monsoon dependence of Indian agriculture, flood-drought cycles, and the impact of global phenomena like El Niño.

Continue reading NCERT Class 9 Geography Chapter 5 – Natural Vegetation and Wildlife to understand how climate influences forest types and biodiversity in India.

FAQs

Q1. What is NCERT Class 9 Geography Chapter 4 about?
It explains India’s climate, monsoon mechanism, seasons and rainfall distribution.

Q2. What are the four seasons of India?
Cold Weather Season, Hot Weather Season, Advancing Monsoon Season and Retreating Monsoon Season.

Q3. What is the average annual rainfall of India?
India receives about 118 cm of average annual rainfall.

Q4. What is El Niño and how does it affect India?
El Niño is a warming of Pacific Ocean waters that can weaken the Indian monsoon and cause drought.

Q5. Why is Chapter 4 important for exams?
It explains the monsoon system and climatic patterns, which are important for school exams and competitive exams like BPSC and UPSC.

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