1. Introduction

• Climate: Sum total of weather conditions & variations over a large area for a long period (>30 years).
• Weather: State of atmosphere over an area at any point of time.
• Elements: Temperature, Atmospheric Pressure, Wind, Humidity, Precipitation.
• Monsoon: Seasonal reversal in wind direction during a year. (Arabic ‘Mausim’ = Season).

2. Climatic Controls (जलवायु नियंत्रण)

There are 6 major controls of climate:

1. Latitude: Temp decreases from Equator to Poles.
2. Altitude: Temp decreases as height increases.
3. Pressure & Wind System: Depends on lat/altitude. Influences rain.
4. Distance from Sea: Moderating influence. Farther = Extreme weather (Continentality).
5. Ocean Currents: Warm/Cold currents affect coastal climate.
6. Relief: Mts act as barriers (Rain shadow vs Windward side).

3. Factors Affecting India’s Climate

• Latitude: Tropic of Cancer divides India into Tropical (South) & Sub-tropical (North).
• Altitude: Himalayas prevent cold winds from Central Asia → Milder winters.
• Winds: India lies in NE Trade Winds region.

4. The Cold Weather Season (Winter)

• Duration: Mid-November to February.
• Coldest Months: December & January.
• Temp decreases from South to North.
• Winds: NE Trade winds prevail (Land to Sea → Dry).
• Tamil Nadu coast gets rain (Sea to Land winds).
• Western Cyclonic Disturbances: From Mediterranean Sea. Cause winter rain (Mahawat) → Good for Rabi crops.

5. The Hot Weather Season (Summer)

• Duration: March to May.
• Heat belt shifts northwards. Temp rises to 45°C in NW India.
• Loo: Strong, gusty, hot, dry winds (daytime).
• Kaal Baisakhi: Localized thunderstorms in West Bengal.
• Mango Showers: Pre-monsoon showers in Kerala/Karnataka (help mangoes ripen).

6. Advancing Monsoon (Rainy Season)

• Duration: Early June to September.
• Low pressure over Northern Plains attracts SE Trade Winds from S. Hemisphere.
• Cross equator → Turn right → SW Monsoon.
• Breaks in Monsoon: Wet & dry spells interspersed.
• Mawsynram: Highest average rainfall in the world.

7. Retreating Monsoon (Transition)

• Duration: October – November.
• Monsoon trough weakens → replaced by high pressure.
• Clear skies + Rise in temperature.
• October Heat: Oppressive weather due to high temp & humidity.
• Cyclones shift to Bay of Bengal → Hit East Coast (Godavari/Krishna/Kaveri deltas).
• Bulk of rainfall on Coromandel Coast occurs now.

8. Distribution of Rainfall

• High (>400 cm): West Coast & NE India.
• Low (<60 cm): W. Rajasthan, Gujarat, Haryana, Punjab, Leh.
• Rest of country: Moderate.
• Snowfall: Himalayan region.

9. Monsoon as Unifying Bond

Despite regional variations, the monsoon provides a rhythmic cycle of seasons.

• Indian landscape, animal/plant life, agricultural calendar, and festivals revolve around it.
• Binds the whole country by providing water for agriculture.
• River valleys act as single units.