Climatic Controls and Factors
Climate questions are among the most repeated in GS-I and in every state exam. Weather is the state of the atmosphere on a day; climate is the average of weather over about 30 years or more. India has a tropical monsoon climate with huge regional variety. Both the controls (permanent factors) and the elements (temperature, pressure, wind, humidity, rainfall) matter.
Why "monsoon"?
The word comes from the Arabic mausim, meaning season. It describes a seasonal reversal of winds. India's climate is called a monsoon climate because winds change direction between summer and winter.
Factors that decide India's climate
| Factor | How it works for India |
|---|---|
| Latitude | The Tropic of Cancer (23.5°N) cuts the country almost in half. The south is tropical; the north is sub-tropical or temperate. |
| Himalayas | Block cold, dry Central Asian winds in winter (so the north plains are warmer than other places at the same latitude) and trap monsoon winds so they give rain. |
| Land and sea distribution | Water on three sides gives a maritime effect on the coast and continentality (extremes) in the interior. |
| Distance from the sea | Mumbai has a small annual range of temperature; Delhi and Jodhpur have a large range. |
| Altitude | Temperature falls about 6.5°C per 1,000 m (normal lapse rate). Shimla, Ooty, Srinagar are cool. |
| Relief | Windward slopes get heavy rain (Western Ghats); leeward rain-shadow zones are dry (Deccan interior, Ladakh). |
| Pressure and wind systems | Seasonal shift of the ITCZ, sub-tropical westerly jet, western disturbances. |
| Upper air circulation | Jet streams, Tropical Easterly Jet, Somali jet (the Findlater jet). |
| El Nino and La Nina, IOD | Ocean-atmosphere events that change monsoon strength year to year. |
Key atmospheric concepts
- ITCZ (Inter-Tropical Convergence Zone): a belt of low pressure near the equator where trade winds meet. In July it shifts north to about 25°N over the Gangetic plain and is then called the monsoon trough.
- Sub-tropical westerly jet stream: in winter flows south of the Himalayas at about 25°-35°N. Its branch brings western disturbances. In summer it moves north of the Himalayas and the Tropical Easterly Jet forms over the peninsula, helping the monsoon.
- Western disturbances: extra-tropical cyclones from the Mediterranean region that bring winter rain and snow to J&K, Himachal, Punjab, Haryana and western Uttar Pradesh. They are good for the rabi wheat crop.
- Walker circulation and ENSO: El Nino (warming of the central-east Pacific) usually weakens the Indian monsoon; La Nina usually strengthens it.
- Indian Ocean Dipole (IOD): positive IOD (warm west Indian Ocean) usually helps the monsoon and can offset El Nino.
- Madden-Julian Oscillation (MJO): an eastward-moving pulse of cloud and rain that causes active and break spells within the monsoon.
Temperature facts
- Highest recorded temperature: about 50.6°C at Alwar (Rajasthan, 1955); Phalodi in Rajasthan recorded about 50°C in 2016 and 2024 readings in the range of 50°C+ have been reported. Treat as "close to 50°C".
- Hottest region is the Thar and northern plains in May-June.
- The coldest inhabited places are Drass and Leh-Ladakh (J&K and Ladakh), where winter minima go below minus 30°C.
Keep practising
Notes are only half the work. Test yourself with questions and discuss doubts with other aspirants.
Prepared for exam revision from NCERT, standard geography textbooks, the Census of India 2011, the India State of Forest Report, IMD, Ministry of Agriculture and other official sources. Maps are schematic teaching maps, not Survey of India maps, and zone boundaries are approximate. Figures such as production, capacity, counts of parks and ports, and census status change, so check the latest official source before relying on them. Found a mistake? Tell us.