Climate ICSE Class 10: The Monsoon, Seasons and Climate Data

What Climate is about

Weightage: CISCE publishes no chapter weightage. Each Part II chapter is one of nine 10-mark questions (2 + 2 + 3 + 3), of which you answer any five; the chapter can also appear in the Part I MCQs and the map of India question.Source: CISCE ICSE 2027 Specimen Question Paper 502, Geography (H.C.G. Paper 2)

Key concepts

Factors affecting the climate of India

1. Latitude: the Tropic of Cancer runs through the middle of India. The south is in the tropics and is hot throughout the year; the north is sub-tropical, with hot summers and cold winters.
2. Altitude: temperature falls with height, so hill stations such as Shimla and Ooty are cooler than places on the plains at the same latitude.
3. Distance from the sea: coastal places such as Mumbai and Chennai have an equable (moderate) climate with a small range of temperature; places far inland such as Delhi have an extreme (continental) climate with a large range.
4. Winds: the monsoon winds reverse direction with the seasons; in winter, western disturbances bring rain to the north-west.
5. The Himalayas: they block the cold, dry winds from Central Asia in winter, and they stop the moist monsoon winds from escaping northwards, forcing them to shed their rain over India.
6. Jet streams: fast westerly winds in the upper atmosphere. In winter the sub-tropical westerly jet lies south of the Himalayas and brings western disturbances to north India; in summer it shifts north of the Himalayas, and an easterly jet over the peninsula is linked with the monsoon's onset.
7. El Niño: an occasional warming of the ocean surface off the coast of Peru in the eastern Pacific. It weakens the Indian monsoon and often causes drought.

Worked example

(2 marks) 'The Himalayas act as a climatic divide.' Give two reasons.

Try it first, then show the solutionSolution

1. They block the cold, dry winds from Central Asia, keeping northern India warmer in winter - 1 mark.
2. They trap the moist south-west monsoon winds, forcing them to shed their rain over India; without them north India would be a dry desert - 1 mark.

Answer: The Himalayas stop the bitterly cold Central Asian winds from entering India in winter, and they act as a barrier to the monsoon winds, making them pour their moisture over India. So they separate India's warm monsoon climate from the cold, dry climate of Central Asia.

Mechanism of the monsoon

The word monsoon comes from the Arabic 'mausim', meaning season. The monsoon is a seasonal reversal of winds.

Summer (south-west monsoon):
1. Land heats faster than the sea. By May, intense heating creates a large area of low pressure over north-western India and Pakistan, while the Indian Ocean to the south is cooler, with higher pressure.
2. The south-east trade winds of the southern hemisphere cross the equator. They are deflected to their right by the earth's rotation and blow from the south-west towards the low pressure over India.
3. Having crossed thousands of kilometres of warm ocean, they are full of moisture and bring heavy rain. The northward shift of the inter-tropical convergence zone and the shift of the westerly jet stream north of the Himalayas help the monsoon to set in.

Winter (north-east monsoon):
1. Land cools faster than the sea. High pressure builds over north-western India and Central Asia, while the seas to the south are warmer, with lower pressure.
2. Winds blow from the land towards the sea, from the north-east. They are dry, except where they cross the Bay of Bengal and pick up moisture, bringing winter rain to the Tamil Nadu coast.

Worked example

(3 marks) Explain how the south-west monsoon winds develop.

Try it first, then show the solutionSolution

1. In summer the land heats rapidly and a low-pressure area forms over north-western India, while high pressure lies over the cooler Indian Ocean - 1 mark.
2. The south-east trade winds cross the equator, are deflected by the earth's rotation and blow from the south-west towards the low - 1 mark.
3. Crossing the warm ocean, they gather moisture and bring heavy rain to India - 1 mark.

Answer: Intense summer heating creates low pressure over north-western India, with higher pressure over the Indian Ocean. The south-east trades cross the equator, are deflected to become south-westerly, and blow towards the low. Having crossed the warm sea, they are moist and give heavy rain.

Hot weather season (March to May)

Temperature: the sun's apparent movement northwards makes temperatures rise from south to north; north-western India reaches 45°C or more in May. Coastal places stay milder.
Pressure: low pressure develops over north-western India.
Winds: winds are variable; hot, dry dusty winds blow in the north.

Local winds and storms:

• Loo: a hot, dry wind blowing in the afternoons over the northern plains (Punjab to Bihar), often causing heat stroke.
• Dust storms (andhis) in Rajasthan and Punjab.
• Kalbaisakhi or Nor'westers: violent evening thunderstorms with rain and hail in West Bengal and Assam in April-May. In Assam they are called 'tea showers'; they help the tea, jute and rice crops.
• Mango showers: pre-monsoon showers in Kerala and coastal Karnataka that help mangoes ripen.
• Blossom (cherry) showers: in Karnataka, helping coffee plants flower.

Worked example

(2 marks) Name the local wind that brings rain to Assam and West Bengal in April. How is it useful?

Try it first, then show the solutionSolution

1. Kalbaisakhi (Nor'westers) - 1 mark.
2. The rain helps tea ('tea showers' in Assam), jute and rice cultivation - 1 mark.

Answer: The Kalbaisakhi or Nor'westers. Their rain benefits the tea gardens of Assam, where they are called tea showers, and the jute and rice crops of West Bengal.

South-west monsoon season (June to September)

The monsoon reaches the Kerala coast around 1 June and covers the whole country by early July (the India Meteorological Department's normal date is about 8 July). Because of the shape of the peninsula, it divides into two branches.

Arabian Sea branch: strikes the Western Ghats, rises and gives very heavy orographic rain on the windward (western) side, such as Mumbai and the Konkan coast. After crossing the Ghats the winds descend and are dry, so the leeward side (for example Pune, east of the Ghats) lies in a rain-shadow area. Further north it reaches Gujarat and Rajasthan, where the Aravalis lie parallel to it and do not block it, so Rajasthan gets little rain.

Bay of Bengal branch: moves north-east towards Myanmar and north-east India; trapped by the funnel-shaped Khasi hills, it gives some of the world's heaviest rain at Mawsynram and Cherrapunji. Blocked by the Himalayas, it turns west along the Ganga valley; rainfall decreases westwards (Kolkata gets more than Patna, Patna more than Delhi) as the winds lose moisture.

Tamil Nadu coast gets little rain in this season because it lies in the rain shadow of the Western Ghats and parallel to the Bay of Bengal branch.

Breaks in the monsoon: dry spells of a few days or weeks within the rainy season.

Worked example

(2 marks) Why does Mumbai receive much more rain than Pune during the south-west monsoon?

Try it first, then show the solutionSolution

1. Mumbai is on the windward side of the Western Ghats; the moist Arabian Sea winds rise and give heavy rain there - 1 mark.
2. Pune is on the leeward side; the descending winds are dry, so it lies in a rain-shadow area - 1 mark.

Answer: Mumbai lies on the windward side of the Western Ghats, where the Arabian Sea branch rises and pours heavy rain. Pune lies on the leeward side, in the rain shadow, where the descending winds are dry.

Retreating monsoon season (October to November)

As the sun moves south, the low pressure over north-western India weakens and shifts to the Bay of Bengal. The south-west monsoon winds withdraw gradually from the north-west by early October and from most of the peninsula by early December.

Conditions: clear skies and rising temperatures after the rains, with high humidity, make the weather oppressive; this is called 'October heat'.

Rainfall: little over most of India, but the east coast, especially Tamil Nadu, gets heavy rain. The north-east winds pick up moisture over the Bay of Bengal and shed it on the Coromandel coast.

Cyclones: tropical cyclones form over the warm Bay of Bengal and strike the eastern coast (Odisha, Andhra Pradesh, Tamil Nadu, West Bengal), bringing very strong winds, heavy rain and storm surges.

Difference from the south-west monsoon: the south-west monsoon blows from sea to land (June-September) and brings rain to most of India; the retreating monsoon withdraws from land to sea (October-November) and brings rain mainly to the east coast.

Worked example

(2 marks) Give two differences between the south-west monsoon and the retreating monsoon.

Try it first, then show the solutionSolution

1. Season and direction: the south-west monsoon (June-September) blows from the sea onto the land from the south-west; the retreating monsoon (October-November) withdraws from the land towards the sea - 1 mark.
2. Rainfall: the south-west monsoon brings rain to most of India; the retreating monsoon gives rain mainly to the east coast, especially Tamil Nadu, and brings cyclones - 1 mark.

Answer: (1) The south-west monsoon (June-September) blows onshore from the south-west; the retreating monsoon (October-November) is the withdrawal of winds from land to sea. (2) The first brings rain to most of India; the second gives rain mainly to the east coast and is marked by cyclones and October heat.

Cold weather season (December to February)

Temperature: temperatures decrease from south to north. The northern plains are cold (often below 10°C in January, with frost at times), while the south remains warm.
Pressure: high pressure over north-western India.
Winds: dry north-east winds blow from land to sea.

Rain:

• Western disturbances: temperate (extra-tropical) cyclones that start over the Mediterranean Sea and are brought eastwards by the westerly jet stream. They give light winter rain to Punjab, Haryana and western Uttar Pradesh, which is very good for rabi crops like wheat, and snowfall in Jammu and Kashmir and Himachal Pradesh.
• North-east monsoon: winds crossing the Bay of Bengal bring winter rain to the Tamil Nadu coast.

Temperate cyclones (western disturbances) cause less damage than tropical cyclones because they are weaker, have lower wind speeds, cover larger areas with light, gentle rain, and form over a cooler sea and travel over land, rather than drawing energy from a warm sea.

Worked example

(2 marks) What causes snowfall in Kashmir in winter? How does it help agriculture in the plains below?

Try it first, then show the solutionSolution

1. Snowfall in Kashmir is caused by western disturbances, temperate cyclones from the Mediterranean - 1 mark.
2. The same disturbances give light winter rain to Punjab and Haryana, which helps the wheat (rabi) crop - 1 mark.

Answer: Western disturbances, temperate cyclones arriving from the Mediterranean region, cause winter snowfall in Kashmir. They also give light winter rain to Punjab and Haryana, which helps the rabi wheat crop.

Distribution of rainfall and interpreting climate data

Rainfall distribution:

• Heavy (over 200 cm): the west coast and Western Ghats, north-eastern India, Andaman and Nicobar Islands.
• Moderate (100-200 cm): the eastern Ganga plain, Odisha, eastern Madhya Pradesh and parts of the eastern peninsula.
• Low (50-100 cm): the western Ganga plain, the interior Deccan.
• Very low (below 50 cm): western Rajasthan (Thar), Ladakh and the leeward side of the Western Ghats in places.

Interpreting a station's climate data:
1. Annual range of temperature = highest monthly temperature - lowest monthly temperature, in °C.
2. Total annual rainfall = sum of the monthly figures, in cm.
3. Coastal or inland: a small range (roughly under 8 to 10°C) shows a coastal, maritime station; a large range shows a continental, inland station.
4. Rainy season and winds: heaviest rain in June-September means the south-west monsoon; heaviest rain in October-December means the north-east (retreating) monsoon on the Tamil Nadu coast.
5. Latitude hint: a cold January (below about 15°C) points to northern India; warm winters point to the south.

Worked example

(3 marks) A station's highest monthly temperature is 33.4°C (May) and lowest 14.2°C (January). It gets 82 cm of rain, mostly in July and August. (a) Find the annual range. (b) Is it coastal or inland? (c) Which winds bring its rain?

Try it first, then show the solutionSolution

1. (a) 33.4 - 14.2 = 19.2°C - 1 mark.
2. (b) A range of 19.2°C is large, so the station is inland (continental), probably in the northern plains - 1 mark.
3. (c) Rain in July-August comes from the south-west monsoon (Bay of Bengal branch, for the northern plains) - 1 mark.

Answer: (a) 19.2°C. (b) Inland, as the range is large. (c) The south-west monsoon.

Climate in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Monsoon Mechanism and the Four Seasons of India

Climate: key facts

Annual range of temperature

Highest monthly mean - lowest monthly mean (in °C)

Always write °C.

Total annual rainfall

Sum of monthly rainfall (in cm)

Seasons

Summer Mar-May; SW monsoon Jun-Sep; retreating Oct-Nov; winter Dec-Feb

Monsoon onset

Kerala about 1 June; whole India by early July (normal date about 8 July)

Local winds

Loo (north plains, hot, dry); Kalbaisakhi (West Bengal, Assam); mango showers (Kerala, Karnataka); blossom showers (Karnataka)

Highest rainfall

Mawsynram and Cherrapunji (Khasi hills, Meghalaya)

Bay of Bengal branch.

Winter rain

Punjab-Haryana: western disturbances; Tamil Nadu: north-east monsoon

Climate: map work

The places on the official CISCE map list for this chapter. Find each one on an outline map of India and practise marking it.

How the board asks Climate

The question patterns to expect, and the method that works for each.

Tricks to remember Climate

Short memory aids. Say each one aloud once, then use it on a question the same day.

• L-A-D-W-H-J-E

  Latitude, Altitude, Distance from sea, Winds, Himalayas, Jet streams, El Niño: 'Let A Dog Walk Home, Just Easy.'

  Use it when: Factors.

• Summer showers by place

  Mangoes in Kerala, coffee blossoms in Karnataka, tea in Assam (Kalbaisakhi).

  Use it when: Local winds.

• Two winter rains

  North-west: western disturbances; south-east: north-east monsoon.

  Use it when: Winter rainfall questions.

• Range tells the coast

  Small range, sea nearby; big range, land all around.

  Use it when: Climate data.

Climate: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In the board paper this is a 10-mark question split into 2 + 2 + 3 + 3 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Climate

The slips examiners see most often, and what to write instead.

• ✗Mistake: Missing units or arithmetic slips in climate data

  CISCE examiners' comments, 2024 and 2025: candidates omitted the unit in the annual range and made calculation errors.

  Wrong working

  Range = 32.6

  Right working

  Range = 41.0 - 8.4 = 32.6°C

  ✓Do this: Write the subtraction and the unit every time.

  Usually costs: 1 mark.

• ✗Mistake: Confusing the retreating monsoon with the north-east monsoon, or giving one difference

  CISCE examiners' comments, 2024: candidates gave only one correct difference and confused the retreating monsoon with the north-east monsoon; in 2025 some wrote 'retreating monsoon' for the rainy-season wind.

  ✓Do this: Retreating = withdrawal of the south-west monsoon in October-November; rainy season = south-west monsoon.

  Usually costs: 1 to 2 marks.

• ✗Mistake: Wrong reason for Mumbai-Pune difference

  CISCE examiners' comments, 2025: candidates chose that R explains A, not grasping that the Western Ghats block the Arabian Sea branch.

  ✓Do this: Always ask: what relief feature lies between the two places?

  Usually costs: The full mark.

• ✗Mistake: Wrong cause of winter snow in Kashmir

  CISCE examiners' comments, 2024: candidates chose tropical cyclones or monsoon winds instead of temperate cyclones.

  ✓Do this: Winter in the north-west = western disturbances = temperate cyclones.

  Usually costs: The full mark.

• ✗Mistake: Describing the Himalayas as dividing temperate from tropical zones

  CISCE examiners' comments, 2024: candidates described the climatic divide as a temperate zone north and tropical south.

  ✓Do this: Explain the two functions: blocking cold winds and trapping monsoon winds.

  Usually costs: 1 to 2 marks.

Practice questions on Climate

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which local wind helps mangoes ripen in Kerala?
   (a) Loo
   (b) Mango showers
   (c) Kalbaisakhi
   (d) Western disturbances

   Hint

   The name says it.

   Answer

   (b) Mango showers.

2. Q2 · 1 mark · MCQBoard level

   Which place receives very heavy rainfall because of the funnel-shaped hills of Meghalaya?
   (a) Jaisalmer
   (b) Mawsynram
   (c) Leh
   (d) Chennai

   Hint

   Khasi hills.

   Answer

   (b) Mawsynram.

3. Q3 · 2 marks · Very short answerHarder board level

   What is El Niño and how does it affect India?

   Hint

   Pacific warming.

   Answer

   El Niño is an occasional warming of the ocean surface off the coast of Peru in the eastern Pacific. It weakens the Indian monsoon, often causing deficient rainfall or drought.

4. Q4 · 2 marks · Very short answerHarder board level

   Why does Rajasthan receive little rain from the Arabian Sea branch?

   Hint

   Aravalis.

   Answer

   The Aravali Range lies parallel to the direction of the Arabian Sea branch, so it does not force the winds to rise and cool; and the hot, dry land reduces condensation. The winds pass on, giving little rain.

5. Q5 · 2 marks · Very short answerBoard level

   What is 'October heat'?

   Hint

   After the rains.

   Answer

   The oppressive weather in October during the retreating monsoon, when skies clear and temperatures rise again while humidity remains high.

6. Q6 · 3 marks · Short answerBoard level

   State three characteristics of the cold weather season in north India.

   Hint

   Temperature, winds, rain.

   Answer

   (1) Low temperatures, decreasing northwards, sometimes with frost. (2) Dry north-east winds blowing from land to sea, with high pressure over the north-west. (3) Light rain from western disturbances in the north-west and snowfall in the hills.

7. Q7 · 3 marks · Short answerHOTS / competency

   How do jet streams affect India's climate in winter and summer?

   Hint

   Position of the westerly jet.

   Answer

   In winter the sub-tropical westerly jet lies south of the Himalayas and steers western disturbances into north-western India, giving winter rain and snow. In summer it shifts north of the Himalayas and an easterly jet develops over the peninsula, which is associated with the sudden onset of the monsoon.

8. Q8 · 3 marks · Case-basedHOTS / competency

   Study: Station P has an annual range of 4°C and maximum rain in November; Station Q has a range of 22°C and maximum rain in July. Identify the type of location and the main rain-bearing winds of each.

   Hint

   Range and rainy month.

   Answer

   P: coastal, on the Tamil Nadu (Coromandel) coast; rain from the north-east (retreating) monsoon. Q: inland, in the northern plains; rain from the south-west monsoon.

9. Q9 · 2 marks · Very short answerBoard level

   Mention two ways in which the loo affects people in the northern plains.

   Hint

   Health and work.

   Answer

   The hot, dry loo can cause heat stroke and dehydration, and it makes outdoor work in the afternoons very difficult.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.When does the monsoon reach Kerala?Show answer

   Around 1 June.

2. 2.What are mango showers?Show answer

   Pre-monsoon showers in Kerala and Karnataka that help mangoes ripen.

3. 3.Why is Pune drier than Mumbai?Show answer

   It lies in the rain shadow of the Western Ghats.

4. 4.Which winds bring winter rain to Tamil Nadu?Show answer

   The north-east monsoon.

5. 5.How is the annual range of temperature found?Show answer

   Highest monthly temperature minus lowest monthly temperature, in °C.

6. 6.What is El Niño?Show answer

   A warming of the eastern Pacific off Peru that weakens the Indian monsoon.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Factors: latitude, altitude, distance from sea, winds, Himalayas, jet streams, El Niño.
• ☐Mechanism: differential heating; low over NW India in summer; SE trades become SW monsoon.
• ☐Summer: loo, dust storms, Kalbaisakhi (tea showers), mango showers, blossom showers.
• ☐SW monsoon: Kerala 1 June; Arabian Sea branch (Western Ghats, rain shadow); Bay of Bengal branch (Mawsynram; decreases westward).
• ☐Retreating monsoon: October heat; cyclones; Tamil Nadu rain.
• ☐Winter: dry NE winds; western disturbances (wheat, snow); NE monsoon in Tamil Nadu.
• ☐Data: range in °C; total in cm; small range = coastal; rainy months tell the wind.

Climate: frequently asked questions