Why does Delhi sizzle at 45°C in June but shiver in January, while Mumbai stays sticky all year? The answer is climate — the long-term mood of the atmosphere. India's climate is called the monsoon type, ruled by winds that reverse with the seasons and bring the rains that feed a billion people.
Weather vs Climate
Weather = day-to-day state of the atmosphere; climate = the average over 30+ years.
Monsoon
From Arabic mausim (season) — seasonal reversal of wind direction over the year.
Six controls
Latitude, altitude, pressure & winds, distance from sea, relief, ocean currents.
Four seasons
Cold weather, hot weather, advancing monsoon, retreating monsoon.
1. Weather and Climate
Weather refers to the state of the atmosphere over an area at any point of time — it can change within hours (sunny morning, rainy afternoon). The elements of weather and climate are the same: temperature, atmospheric pressure, wind, humidity and precipitation. Climate is the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years). India has a great diversity of weather, but as a whole the climate is described as the "monsoon" type, since this kind of climate is found mainly in South and Southeast Asia.
2. Climatic Controls (Six Factors)
The climate of any place depends on six major controls. (i) Latitude: The Tropic of Cancer passes through the middle of India, so the southern half lies in the tropical zone and the northern half in the sub-tropical zone — this gives India both tropical and temperate climate features. (ii) Altitude: As you go higher, the atmosphere becomes less dense and temperature falls. That is why hills are cooler in summer (Shimla is cooler than Delhi). (iii) Pressure and Winds: The pressure and wind system depend on latitude and altitude, controlling temperature and rainfall. (iv) Distance from the Sea: Coastal areas like Mumbai have a moderate (maritime) climate, while interiors like Delhi face extremes of heat and cold (continentality). (v) Ocean Currents: Currents along with onshore winds affect the climate of coastal areas. (vi) Relief features: High mountains act as barriers; the Himalayas block cold winds from Central Asia, and windward slopes receive heavy rain while leeward slopes stay dry.
3. Factors Affecting India's Climate
Apart from the general controls, India's climate is shaped by latitude, altitude (the Himalayas keep the subcontinent warmer than Central Asia), and the pressure and wind systems. Three special features matter: (a) surface distribution of pressure and winds, (b) the upper air circulation caused by factors controlling global weather such as the inflow of different air masses and jet streams, and (c) the inflow of western cyclonic disturbances (known as western disturbances) and tropical depressions. The jet streams are fast flowing, narrow air currents in the upper atmosphere. The subtropical westerly jet stream blows south of the Himalayas in winter and brings western disturbances; the tropical easterly jet stream blows over peninsular India in summer.
4. The Indian Monsoon
The monsoon is the heartbeat of India. It involves a complete reversal of winds with the seasons. The factors behind the monsoon include: the differential heating and cooling of land and water (low pressure over land in summer, high over the sea); the shift of the position of the Inter Tropical Convergence Zone (ITCZ) in summer over the Ganga plain; the presence of the high-pressure area east of Madagascar; the intense heating of the Tibetan plateau in summer; and the movement of the westerly jet stream and the tropical easterly jet stream. Two more phenomena affect the monsoon: the El Nino (a warm ocean current off the Peru coast that can weaken the monsoon) and the Southern Oscillation (SO) — together studied as ENSO.
5. Onset and Withdrawal of the Monsoon
The monsoon has a duration of about 100 to 120 days from early June to mid-September. Its arrival is sudden and is called the burst of the monsoon, marked by a violent rise in rainfall. The monsoon arrives at the southern tip of the Indian peninsula generally by the first week of June. It then splits into two branches: the Arabian Sea branch and the Bay of Bengal branch. The withdrawal or the retreat of the monsoon is a more gradual process, beginning in northwestern states by early September and clearing the southern peninsula by early December.
6. The Four Seasons
India has four main seasons. (1) The Cold Weather Season (Winter, mid-Nov–Feb): Temperatures decrease from south to north. Days are warm, nights cold; northern plains get rain from western disturbances, vital for the rabi crops. (2) The Hot Weather Season (Summer, Mar–May): Temperatures rise sharply; a striking feature is the loo — strong, hot, dry winds in the north. Localised storms bring mango showers (Kerala & Karnataka) and the Kaal Baisakhi (West Bengal & Assam). (3) Advancing Monsoon (Rainy Season, June–Sept): The southwest monsoon brings most of India's rain; rainfall is not continuous but has breaks. (4) Retreating/Post Monsoon (Oct–Nov): Clear skies, rising temperature and high humidity create oppressive weather called "October heat"; this season is associated with cyclones on the eastern coast.
7. Distribution of Rainfall
Rainfall is very unevenly distributed. The western coast and northeastern India receive over 400 cm a year, while parts of western Rajasthan, Ladakh and the interior of the Deccan plateau get less than 60 cm. Mawsynram in Meghalaya receives the highest rainfall in the world. As a rule, rainfall decreases from east to west in the northern plains. The seasonal and regional variation of rainfall causes both floods in some areas and droughts in others in the same year.
8. Monsoon as a Unifying Bond
The monsoon is described as the unifying bond of India. The Indian landscape, its plant, animal and aquatic life, and the entire agricultural calendar — together with the rhythm of festivals — are governed by the monsoon. Year after year, people of India eagerly await the arrival of the monsoon, which provides water to set agricultural activities in motion. It binds the whole country together with its uncertainties, irregularities and abundance.
- Climate = average weather over 30+ years; weather = day-to-day.
- Monsoon word from Arabic mausim = season; involves seasonal reversal of winds.
- Six climatic controls: Latitude, Altitude, Pressure & Winds, Distance from sea, Ocean currents, Relief.
- Monsoon onset: southern tip by first week of June; duration 100–120 days.
- Two branches: Arabian Sea branch & Bay of Bengal branch.
- Mawsynram (Meghalaya) — highest rainfall in the world (>400 cm).
- Western Rajasthan & Ladakh — less than 60 cm rainfall.
- Loo = hot dry summer wind; Mango showers, Kaal Baisakhi, October heat.
- El Nino + Southern Oscillation = ENSO, affects monsoon strength.
"The monsoon is considered the unifying bond of India." Explain. (5 marks)
- Define the monsoon as the seasonal reversal of winds bringing rain over the subcontinent.
- State that the whole Indian agricultural calendar depends on it.
- Give supporting points: landscape, plant & animal life, and water supply.
- Add the human/cultural angle — festivals and people awaiting the rains.
- Conclude that despite its uncertainties it binds the country together.
Explain the six major controls of the climate of any place. (5 marks)
- Name all six controls first so the examiner sees full coverage.
- Explain latitude and altitude (temperature effects).
- Explain pressure & winds and distance from the sea.
- Explain ocean currents and relief features.
- Give one Indian example for each where possible.
Remember the six climatic controls with "LAP-DOR": Latitude, Altitude, Pressure & winds, Distance from sea, Ocean currents, Relief. And the four seasons in order — Cold → Hot → Advancing → Retreating monsoon (just follow the calendar from January to December).
Do not confuse weather with climate — weather is short-term and daily, climate is the long-term average over 30+ years. Also keep the monsoon branches straight: the Arabian Sea branch and the Bay of Bengal branch are two separate branches of the same southwest monsoon, not two different monsoons.
Q1. What is meant by "monsoon"? Why is India's climate called the monsoon type?
Answer: The word monsoon is derived from the Arabic word mausim, meaning season. The monsoon refers to the seasonal reversal in the wind direction during a year. In summer the winds blow from the sea to the land (southwest monsoon) bringing rain, while in winter they blow from the land to the sea (northeast monsoon). India's climate is called the "monsoon type" because the entire year's weather and the agricultural cycle are dominated by these seasonal monsoon winds, a pattern typical of South and Southeast Asia.
Q2. Describe the "advancing monsoon" (rainy) season in India.
Answer: The advancing monsoon or rainy season begins in early June and lasts till September. By this time the low-pressure conditions over the northern plains intensify and attract the southwest monsoon winds from the sea. The monsoon enters with a sudden burst, causing a violent rise in rainfall over several days. The winds split into the Arabian Sea branch and the Bay of Bengal branch. Rainfall in this season is not continuous — it has wet and dry spells called breaks in the monsoon. This season provides most of India's annual rainfall and is crucial for kharif crops.
Q3. What are jet streams and how do they affect India's climate?
Answer: Jet streams are a narrow belt of high-altitude (above 12,000 m) fast-blowing westerly winds in the upper atmosphere. Their speed varies from about 110 km/h in summer to 184 km/h in winter. The subtropical westerly jet stream blows over India south of the Himalayas in winter and is responsible for bringing western disturbances, which cause winter rain in the northwestern plains (good for the rabi crop). In summer the jet shifts north and the tropical easterly jet stream blows over peninsular India, helping the onset of the southwest monsoon.
Q4. Discuss the uneven distribution of rainfall in India and its effects.
Answer: Rainfall in India is highly uneven in both space and time. Areas such as the western coast and northeastern India receive more than 400 cm of rain a year, with Mawsynram in Meghalaya recording the highest rainfall in the world. In contrast, western Rajasthan, Ladakh and the interior of the Deccan plateau receive less than 60 cm. In general, rainfall decreases from east to west across the northern plains. Because the rain comes only in a few months and varies year to year, the same country experiences floods in some regions and droughts in others, often in the same season. This uncertainty makes agriculture risky and creates a need for irrigation and water management.
- ✅ Weather = daily; Climate = average over 30+ years; India = monsoon type.
- ✅ Six controls (LAP-DOR): Latitude, Altitude, Pressure & winds, Distance from sea, Ocean currents, Relief.
- ✅ Monsoon = seasonal reversal of winds; onset by first week of June, lasts 100–120 days, splits into Arabian Sea and Bay of Bengal branches.
- ✅ Four seasons: Cold, Hot (loo, mango showers, Kaal Baisakhi), Advancing monsoon, Retreating monsoon (October heat, cyclones).
- ✅ Rainfall very uneven (Mawsynram >400 cm vs Rajasthan <60 cm); monsoon is the unifying bond of India.
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