Climate & Weather
Climate
- Sum total of weather conditions and variations over a large area for a long period (more than 30 years).
Weather
- State of the atmosphere over an area at any point of time.
Elements of climate & weather:
- 🌡️ Temperature
- Atmospheric pressure
- Wind
- Humidity
- Precipitation
Climate of India
- India has a Monsoon-type climate.
- This type of climate is mainly found in South and Southeast Asia.
- India has overall unity in its climate pattern, but there are considerable regional variations.
- Two important elements:
- Temperature
- Precipitation
Regional Variation in Temperature 🌡️
| Region | Temperature example |
|---|---|
| Rajasthan Desert (summer) | Up to 50°C |
| Pahalgam, J&K (summer) | Around 20°C |
| Drass, J&K (winter night) | As low as –45°C |
| Thiruvananthapuram (winter) | Around 22°C |
This shows the wide regional variation in temperature across India.
❓ Do You Know?
Origin of the word Monsoon
- The word Monsoon is derived from the Arabic word “mausim”, meaning season.
- Monsoon refers to the seasonal reversal in wind direction during a year.
⛵Hippalus uses the monsoon winds for direct sailing to India c. 45–47 CE
•Kushan Empire emerges as a major power 1st–2nd century CE
•Kanishka I's reign usually placed around 2nd century CE
•Kanishka becomes a major Kushan ruler c. 2nd century CE
🌡️ Day & Night Temperature
- Thar Desert: Very large difference between day and night temperatures.
- Day → may rise to 50°C
- Night → may fall to nearly 15°C
- Andaman & Nicobar Islands and Kerala: Very small difference between day and night temperatures.
Precipitation 🌨️❄️⛈️
Precipitation means water falling from the atmosphere to the Earth’s surface.
Types of Precipitation 🌧️
•Rainfall 🌧️ – Water falls as liquid droplets.
•Snowfall ❄️ – Water falls as ice crystals or snowflakes.
•Sleet 🌨️ – Small ice particles formed when raindrops freeze.
•Hail 🧊 – Balls/lumps of ice falling during thunderstorms.
Precipitation varies in:
- Form
- Amount
- Seasonal distribution
Important examples:
Q. [Homework] Watch the Kashmir tourism advertisement at home and read about PoK (Pakistan-occupied Kashmir). Do you think India will be able to bring this region under its control from Pakistan?
- Upper Himalayas → precipitation mainly in the form of snowfall
- Most of the rest of India → mainly rainfall.
- Meghalaya → more than 400 cm rainfall.
- Ladakh & western Rajasthan → less than 10 cm rainfall.
- Most parts of India receive rainfall mainly from June to September.
- Climate → Long-term atmospheric conditions (>30 years)
- Weather → Atmospheric condition at a particular time
- India → Monsoon-type climate
- Monsoon → Seasonal reversal of winds
- Mausim → Arabic word meaning season
- Highest rainfall mentioned → Meghalaya (>400 cm)
- Very low rainfall → Ladakh & western Rajasthan (<10 cm)
- Main rainy season → June–September
- Highest summer temperature example → Rajasthan (50°C)
- Lowest winter temperature example → Drass (–45°C)
🌍 Atmospheric Pressure & Wind
Atmospheric Pressure
•Atmospheric pressure is the pressure exerted by the weight of air on the Earth's surface.
•Change with altitude
•Pressure falls rapidly as we go higher in the atmosphere.
•It is highest at sea level.
•Atmospheric pressure decreases with altitude.
•Horizontal distribution
•Gravity
•The horizontal distribution of air pressure is influenced by air temperature at a given place.
Effect of Temperature on Air Pressure
☀️ High Temperature
Air gets heated → rises → Low Pressure
In areas with high temperatures, air heats up and rises.
This creates a low-pressure area.
Low pressure is associated with cloudy skies and wet weather.
Low Temperature
Air becomes cold → becomes heavy → sinks → High Pressure
In areas with lower temperatures, air is cold.
Cold air becomes heavier and sinks.
This creates a high-pressure area.
High pressure is associated with clear and sunny skies.
Wind
Wind is the movement of air from a high-pressure area to a low-pressure area.
Wind can be gentle or strong.
Its direction is influenced by the Earth's rotation.
Examples
Gentle wind can blow dry leaves down the pavement.
It can gently blow away dust particles.
Strong winds during a storm can uproot trees.
Very strong winds can make it difficult to walk against them.
Diagram: High Pressure → Low Pressure
Rule:
Wind flows from HIGH pressure → LOW pressure.
Don't Miss Out
How are winds named?
Winds are named after the direction from which they blow.
Example:
WEST ───────> EAST= WESTERLY
WIND
So, a wind blowing from the west is called a westerly wind.
🌊 Land Breeze & Sea Breeze
Land breeze and sea breeze are local winds found mainly in coastal areas. They are caused by the unequal heating and cooling of land and sea.
☀️Sea Breeze — During the Day
A sea breeze is a local wind that blows from the sea towards the land during the day.
Process:
1. ☀️ During the day, land heats up faster than the sea.
2. Air over the land becomes warmer and rises.
3. This creates a low-pressure region over the land.
4. The sea remains relatively cooler, with higher pressure.
5. Cool air moves from sea → land.
6. This movement of air is called a sea breeze.
🌙 Land Breeze — During the Night
A land breeze is a local wind that blows from the land towards the sea during the night.
Process:
1. 🌙 At night, land cools faster than the sea.
2. Air over the sea remains warmer and rises.
3. This creates lower pressure over the sea.
4. The land becomes cooler, producing higher pressure.
5. Cool air moves from land → sea.
6. This movement of air is called a land breeze.
Seasons in India
India experiences four main seasons, as recognised by the India Meteorological Department (IMD):
❄️ Winter Season
Period: December – early April
Coldest months: December and January.
North-west India: about 10–15°C.
South-east/mainland India: about 20–25°C.
Temperatures increase towards the equator.
☀️ Summer / Pre-monsoon Season
Period: April – June/July
April is the hottest month in western and southern regions.
Inland India may experience temperatures of 32–40°C.
Temperature rises considerably before the monsoon.
🌧️ Monsoon / Rainy Season
Period: June – September
Dominated by the South-West Monsoon.
Monsoon rain generally begins in late May or early June.
It gradually spreads across the country.
Rainfall is the main feature of this season.
🍂 Post-monsoon / Retreating Monsoon
Period: October – December
The monsoon retreats from northern India beginning in October.
October and November are generally clearer in north-western India.
South India receives significant rainfall during this period.
Winter → Summer → Monsoon → Post-monsoon
❄️ → ☀️ → 🌧️ → 🍂
Note: Traditionally, the Indian calendar also recognises six seasons (Ritu): Vasanta, Grishma, Varsha, Sharada, Hemanta, and Shishira.
Think About It
Hindustani Classical music associates certain ragas with specific seasons. Find out which ragas are connected to each season with the help of your elders and teachers.
Season (Ritu) Some associated Hindustani ragas
🌸 Vasanta -Vasant, Bahar
☀️ Grishma -Deepak (traditionally associated)
🌧️ Varsha -Malhar, Miyan ki Malhar, Megh
🍂 Sharada -Marwa, Puriya
🌫️ Hemanta - Hemant, Hindol
❄️ Shishira -Bhairav, Lalit
DON’T MISS OUT
Kautilya’s Arthaśāstra contains records of scientific measurements of rainfall and their practical application in managing the country’s revenue and relief efforts.
🌧️ Monsoon
1. Meaning of Monsoon
The climate of India is strongly influenced by monsoon winds.
Ancient sailors noticed the seasonal reversal of wind direction while travelling to India.
Arab traders named this seasonal reversal “monsoon”.
The word monsoon is derived from the Arabic word mausim, meaning “season.”
> Monsoon: Seasonal reversal in the direction of winds during the year.
Ancient Knowledge of Monsoon
Since crop production often depended on seasonal monsoon rainfall, ancient Indians developed methods to predict rainfall.
Krishiparāśara and Brihatsaṃhitā describe methods of rainfall prediction.
Krishiparāśara: Its main technique was based on the positions of the Moon and the Sun in the sky.
Varāhamihira, in the Brihatsaṃhitā, considered lunar mansions (nakshatras) for predicting seasonal rainfall.
Even today, many farming practices in India are based on these ancient methods.
Types of Monsoon Winds
Monsoon winds are seasonal winds and can be categorised into:
1.South-West Monsoon ☔
Also called: Summer Monsoon
Period: June–September
Wind movement: Sea → Land
The winds blow from:Indian Ocean,Arabian Sea,Bay of Bengal
Why does it occur?
1. During summer, the landmass of India heats up faster than the surrounding oceans.
2. This creates a low-pressure area over the Indian subcontinent.
3. The surrounding ocean remains relatively cooler and has high pressure.
4. Winds move from high-pressure areas → low-pressure areas.
5. Therefore, moist winds blow from the ocean towards the land, bringing rainfall.
The South-West Monsoon accounts for most of the rainfall in India throughout the year.
Diagram:
The North-East Monsoon is the seasonal wind system that occurs mainly from October to February.
Direction: Winds blow from the north-east towards the south-west, generally from land to sea.
Cause: During winter, the Indian landmass cools faster than the surrounding oceans.
Pressure: High pressure develops over the land.
Rainfall: These winds pick up moisture from the Bay of Bengal and bring important rainfall to the Tamil Nadu (Coromandel) Coast.
Main period: October–February
Diagram:
Nakshatras are a way of dividing the sky into 27 equal parts along the path travelled by the Moon.
Each part is linked to a star or group of stars.
The Moon takes about 27 days to go around the Earth relative to the stars.
Therefore, it moves through approximately one nakshatra each day.
They are called “lunar mansions” because it is like the Moon staying in a different “house” in the sky each night.
The 27 Nakshatras (Lunar Mansions) are: Ashwini, Bharani, Krittika, Rohini, Mrigashira, Ardra, Punarvasu, Pushya, Ashlesha, Magha, Purva Phalguni, Uttara Phalguni, Hasta, Chitra, Swati, Vishakha, Anuradha, Jyeshtha, Mula, Purva Ashadha, Uttara Ashadha, Shravana, Dhanishta, Shatabhisha, Purva Bhadrapada, Uttara Bhadrapada, and Revati.
- During winter, cold and dry winds blow from land towards the sea.
- These winds generally do not bring rainfall to most parts of India.
- When the north-east monsoon winds pass over the Bay of Bengal, they absorb moisture.
- They bring rainfall to the eastern coast of India, especially:
- Tamil Nadu
- Andhra Pradesh
- Parts of Karnataka
- Therefore, the winter monsoon is important for rainfall in south-eastern India.
🌾 Importance of Monsoon in India
The monsoon plays a vital role in the lives and economy of people.
Agriculture
- A large part of Indian agriculture depends on monsoon rainfall.
- Farmers depend on rainfall for sowing and growing crops.
- A good monsoon helps ensure sufficient food production.
Water supply
- Monsoon rainfall provides water to:
- Rivers
- Reservoirs
- Wells
Daily life & economy
- Monsoon affects:
- Transport
- Employment
- Festivals
- Rural livelihoods
- Overall economy
Problems of irregular monsoon
- Excessive rainfall → floods
- Weak/insufficient monsoon → droughts
Thus, the monsoon greatly influences India's economy, lifestyle and livelihoods.
Monsoon in Ancient Indian Literature
- Kalidasa, in his famous work Meghadutam, written around the 5th century CE, mentioned:
- The date of monsoon onset over central India
- The path followed by monsoon clouds
🌦️ National Monsoon Mission (NMM)
- The National Monsoon Mission (NMM) is associated with the Ministry of Earth Sciences, Government of India.
- It has developed advanced weather and climate prediction models.
- Main objective: Improve monsoon predictions for India over different time periods.
Key aim:
Better monsoon prediction → better planning → reduced impact of weather-related problems.
🌍 Mission Mausam
Mission Mausam is designed to strengthen India's position in weather and climate sciences.
Main objectives:
- Make India “Weather Ready” and “Climate Smart”.
- Improve:
- Weather services
- Climate services
- Observation
- Modelling
- Forecasting
- Provide timely and accurate information.
Applications
The information is useful for sectors such as:
- 🌾 Agriculture
- 🚨 Disaster management
- 🏘️ Rural development
- Other weather-sensitive activities
🌍 Climate Change —
Climate change refers to long-term changes in weather patterns, such as:
Temperature
Rainfall
Wind
It is one of the most urgent challenges facing the Earth today.
In the present context, climate change is caused mainly by human activities.
Major Human Causes
🔥 Burning of fossil fuels
🌳 Deforestation
🏭 Industrial pollution
These activities release gases such as carbon dioxide (CO₂) into the atmosphere
Greenhouse Gases
Human activities increase the concentration of greenhouse gases in the atmosphere.
Carbon dioxide (CO₂)
Methane (CH₄)
Nitrous oxide (N₂O)
Water vapour
Q. How they affect climate
Human activities → More greenhouse gases → Heat gets trapped → Global temperature rises → Climate change
Effects of Climate Change
Climate change can lead to:
🌊 More frequent floods
☀️ Droughts
🧊 Melting of glaciers
🌊 Rising sea levels
🐾 Loss of biodiversity
Effects on human life
Climate change affects:
Ecosystems
Human health
Agriculture
Livelihoods
Almost all sections of the population, including women and children.
Tackling Climate Change
Addressing climate change requires collective efforts.
Important measures:
Reduce carbon footprints
Use renewable energy
Protect forests
Adopt sustainable lifestyles
🔎 LET'S EXPLORE
My Carbon Footprint
Carbon Footprint — Meaning
Carbon footprint is the total amount of greenhouse gases released into the atmosphere as a result of human activities, such as:
Energy use
Transportation
Production of goods and services
Step 1: My Daily Habits
A. Transport
Habit Impact
Walking / using a cycle = 🟢 Low impact
Public transport / carpool =🟡 Medium impact
Using private cars even for short distances = 🔴 High impact
Taking flights more than twice a year = 🔴 Very high impact
B. Electricity Use
Always switching off lights, fans, etc. when not in use =🟢 Low impact
Sometimes forgetting to switch off appliances= 🟡 Medium impact
Frequently leaving electrical appliances switched on = 🔴 High impact
C. Water Use
Using water judiciously helps reduce environmental impact.
Example given: using just one bucket of water for bathing → Low impact
Punjab Floods 2025: A Case Study
•Heavy monsoon rains
•Consecutive swelling of the Sutlej, Beas and Ravi rivers.
Large parts of the state were affected, including:
Villages
Agricultural fields
Houses
Roads and bridges
Although water began to recede in some places and relief operations were carried out, the overall impact was devastating.
The floods caused:
Heavy economic losses
Social disruption
Environmental damage
The situation highlighted the need for better flood management and preparedness.
The floods resulted from both natural and human-made factors.
Natural Causes
Punjab received very heavy monsoon rainfall in 2025.
Western disturbances intensified the rainfall by bringing additional moisture and rain.
Heavy rain also occurred in Himachal Pradesh and Jammu & Kashmir.
Major rivers of Punjab—Sutlej, Beas, Ravi and Ghaggar—were already flowing at high levels.
Additional rainfall and water from the hills caused the rivers to overflow.
This resulted in severe flooding in many parts of Punjab.
Human-made Causes
Weak and old river embankments (dhusi bandh) could not stop rising floodwater.
Houses and farms were built too close to rivers, reducing natural space for floodwater.
Silt, mud and other deposits reduced the capacity of rivers and dams to hold and carry water.
In some areas, flood warnings were late or not clearly communicated.
These factors increased the damage caused by the floods.
Effects of the Floods in Punjab
Many people lost their lives.
Thousands of people had to leave their homes and move to relief camps for safety.
Large areas of farmland were submerged.
Crops such as paddy were severely damaged.
Poultry and dairy farms were damaged or destroyed.
Many animals, including cows, buffaloes and chickens, became sick or died.
Roads, bridges, border fences and public buildings were damaged.
Murky standing water caused health problems.
It increased the risk of waterborne diseases and created sanitation problems.
Revision
Heavy monsoon + Western disturbances + Rivers swell +River overflow =Punjab floods
Western cyclonic disturbances are non-monsoonal extratropical storm systems that originate over the Mediterranean region and bring vital winter rain and snow to the northwestern parts of the Indian subcontinent.
The Subtropical Westerly Jet Stream carries these eastward-moving systems across Iran, Afghanistan, and Pakistan.
Now think why
a. Why does Thiruvananthapuram have an equable climate?
It is close to the equator.
It is located near the sea, which moderates temperature.
Its annual temperature range is very small—about 2.5°C (26.2°C to 28.7°C).
b. Why does Chennai receive more rainfall after the monsoon is over in most parts of India?
Chennai receives most of its rainfall during the retreating/North-East Monsoon. The winds cross the Bay of Bengal, pick up moisture and bring heavy rainfall to Tamil Nadu and the south-eastern coast, especially in October–December.
c. Why does Leh have moderate precipitation almost throughout the year?
Leh is located at a high altitude (3506 m) and in a rain-shadow region of the Himalayas. The moisture-laden monsoon winds do not reach Leh effectively, so it receives very little precipitation, spread over the year.
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