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English · हिन्दी · తెలుగు · தமிழ் · മലയാളം · मराठी · ಕನ್ನಡ

Quick recap: the climate of India on one page

मराठीत स्पष्टीकरण

Climate of India · Quick recap · Fact-checked on · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

All three parts condensed for quick revision: how the monsoon works; the four seasons, local storms and cyclones; and rainfall, its variability, climatic regions and IMD's forecasts.

Each idea is explained first in Marathi (मराठी), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Marathi and revise it in English.

आपले हवामान उष्णकटिबंधीय मान्सून प्रकारचे: हिवाळ्यात जमिनीकडून समुद्राकडे, उन्हाळ्यात समुद्राकडून जमिनीकडे वारे उलटतात — तेच पाऊस कधी, कुठे हे ठरवतात. अक्षांश, हिमालय, समुद्रापासूनचे अंतर, भूरचना हे त्याला आकार देतात. हिमालय घराच्या कुंपणभिंतीसारखा थंड वारा अडवतो आणि उन्हाळ्यातले दमट वारे आत धरून ठेवतो. तीन भाग: यंत्रणा, चार ऋतू, पावसाचा आकृतिबंध–अंदाज. (→ English: monsoon; tropical monsoon climate · हिन्दी: मानसून; उष्णकटिबंधीय मानसूनी जलवायु)

In exam EnglishIndia has a tropical monsoon climate: a seasonal reversal of winds, from land to sea in winter and from sea to land in summer, decides when and where the country gets its rain. Latitude, the Himalaya, distance from the sea and relief shape it. The Himalaya keep out Central Asian cold in winter and hold the moist winds in during summer, which is why South Asia behaves as one climatic unit. The chapter moves in three steps: how the monsoon works (Part 1), the four seasons it creates (Part 2), and the resulting pattern of rainfall, its reliability and its forecasting (Part 3).

भाग 1: हिवाळ्यात वायव्येकडे जास्त दाब, कोरडे वारे, हिमालयाच्या दक्षिणेला पश्चिमी जेट. उन्हाळ्यात वायव्येकडे कमी दाब; आंतर उष्णकटिबंधीय अभिसरण क्षेत्र उत्तरेकडे सरकून गंगेच्या मैदानावर द्रोणी; आग्नेय व्यापारी वारे विषुववृत्त ओलांडून नैऋत्य वारे. वर जेट प्रवाह हिमालयाच्या उत्तरेला, 15° जवळ पूर्वी जेट, तापलेले तिबेट. केरळात 1 जून, सर्व देशात 8 जुलै; द्रोणी पायथ्याकडे सरकली की खंड; एल निनो कमजोर करतो; 17 सप्टेंबर ते 15 ऑक्टोबर माघार. (→ English: Inter-Tropical Convergence Zone; jet stream; monsoon onset · हिन्दी: अंतःउष्णकटिबंधीय अभिसरण क्षेत्र; जेट धारा; मानसून का आगमन)

In exam EnglishPart 1, how the monsoon works: in winter, high pressure over north-west India sends dry winds off the land while the westerly jet flows south of the Himalaya. In summer a strong low forms over the north-west, the Inter-Tropical Convergence Zone is pulled north into the monsoon trough over the Ganga plain, and the south-east trades cross the equator and are turned into south-westerlies by the Coriolis force, helped by the Somali jet. Aloft, the westerly jet stream shifts north of the Himalaya, a tropical easterly jet appears near 15°N, and the heated Tibetan plateau strengthens the circulation. The monsoon reaches Kerala about 1 June and covers India by about 8 July (2020 normal dates); breaks come when the trough moves to the foothills; El Niño tends to weaken it and a positive Indian Ocean Dipole to help; withdrawal runs from about 17 September to 15 October.

भाग 2: हिवाळ्यात उत्तरेत दव गोठणे, धुके, थंडीची लाट; पश्चिमी विक्षोभ गव्हासारख्या रब्बी पिकांना पाऊस आणि बर्फ देतो. उन्हाळ्यात उष्णतेचा पट्टा दख्खनकडून वायव्येकडे; लू, धुळीची वादळे; दिलासा म्हणून बंगाल–आसाम–ओडिशात कालबैसाखी, केरळ–कर्नाटक किनाऱ्यावर आंब्याच्या सरी, कॉफी मळ्यांत मोहोराच्या सरी. नैऋत्य हंगामात अरबी समुद्र शाखा घाटावर प्रतिरोध पर्जन्य पाडते, दख्खन पर्जन्यछायेत; उपसागर शाखा मेघालयाला भिजवून कोलकाता ते दिल्ली कमजोर होत जाते. (→ English: western disturbance; kalbaisakhi (nor'wester); orographic rainfall · हिन्दी: पश्चिमी विक्षोभ; काल बैसाखी; पर्वतीय वर्षा)

In exam EnglishPart 2, the seasons: the cold season (December to February) brings frost, fog and cold waves to the north, while each western disturbance, steered from the Mediterranean region by the westerly jet, gives rain and snow valuable for rabi crops. The hot season (March to May) moves the heat belt from the Deccan to the north-west and brings the loo and dust storms; local storms give relief: kalbaisakhi (nor'wester) in West Bengal, Assam and Odisha ('bardoli chheerha' in Assam), mango showers on the Kerala and Karnataka coasts and blossom showers in the coffee areas. In the south-west monsoon season (June to September) the Arabian Sea branch drops orographic rain on the Western Ghats and leaves the Deccan in rain shadow; the Bay of Bengal branch drenches Meghalaya and then weakens westward along the Ganga plain, from Kolkata to Delhi.

जून–सप्टेंबरमध्ये तमिळनाडूचा किनारा जवळजवळ कोरडा — घाटाच्या मागे, उपसागर शाखेला समांतर. परतीचा मान्सून काळात कमी दाब उपसागराकडे; उत्तरेत 'ऑक्टोबर हीट'; ऑक्टोबर–डिसेंबरचा ईशान्य पाऊसच कोरोमंडल किनाऱ्याचा मुख्य पाऊस. उष्णकटिबंधीय चक्रीवादळ एप्रिल–मे किंवा बहुधा ऑक्टोबर–डिसेंबरमध्ये; उपसागरातच जास्त; वादळी लाटेमुळे सर्वाधिक नुकसान; दिल्लीचे IMD केंद्र नावे देते. (→ English: retreating monsoon; north-east monsoon; tropical cyclone · हिन्दी: लौटता मानसून; उत्तर-पूर्व मानसून; उष्णकटिबंधीय चक्रवात)

In exam EnglishThe Tamil Nadu coast stays fairly dry from June to September, being on the leeward side of the Ghats and parallel to the Bay branch. In the retreating monsoon season (October and November) the low moves to the Bay of Bengal, north India feels 'October heat', and the north-east monsoon brings the Coromandel coast its main rain from October to December. A tropical cyclone can strike in April–May or, more often, October–December; the Bay of Bengal has far more than the Arabian Sea, storm surge does most of the damage, and IMD's Regional Specialised Meteorological Centre in New Delhi names the cyclones of the north Indian Ocean.
Climate of India at a glance
SeasonMonthsKey features
Cold weatherDecember–FebruaryHigh pressure in the north-west, dry offshore winds; western disturbances bring rain and snow; fog, frost, cold waves
Hot weatherMarch–MayHeat low from the Thar; loo and dust storms; kalbaisakhi, mango and blossom showers
South-west monsoonJune–SeptemberOnset in Kerala about 1 June; Arabian Sea and Bay of Bengal branches; rain shadow in the Deccan; dry Tamil Nadu coast
Retreating monsoonOctober–NovemberOctober heat in the north; north-east monsoon on the Coromandel coast (to December); main cyclone season

भाग 3: 200 सेंमीहून अधिक पश्चिम किनारा–घाट, मेघालय–ईशान्य, पूर्व हिमालयाचा पायथा; 50 पेक्षा कमी पश्चिम राजस्थान, कच्छ, लडाख. विचलन गुणांक ओल्या भागात कमी, कोरड्या भागात 50% पेक्षा जास्त. 25% हून अधिक तूट = हवामानशास्त्रीय दुष्काळ. मैदानात उष्णतेची लाट 40°C + 4.5°C किंवा 45°C; ढगफुटी तासाला 100 मिमी. कोपेन: पश्चिम किनारा Amw, कोरोमंडल As, द्वीपकल्प Aw. दीर्घकालीन सरासरी सुमारे 87 सेंमी; सामान्य 96–104%, तूट 90 च्या खाली, अतिरिक्त 110 च्या वर; पहिला अंदाज एप्रिलच्या मध्यात. (→ English: long period average (LPA); coefficient of variation · हिन्दी: दीर्घावधि औसत; विचरण गुणांक)

In exam EnglishPart 3, rainfall and forecasting: over 200 cm falls on the west coast and Western Ghats, in Meghalaya and the north-east and along the eastern sub-Himalaya; under 50 cm in western Rajasthan, Kachchh and Ladakh. The coefficient of variation is lowest where rain is heaviest and above 50 per cent in the driest areas. IMD calls a shortfall of more than 25 per cent a meteorological drought. On the plains a heat wave means at least 40°C and 4.5°C above normal, or 45°C; a cloudburst is about 100 mm or more in an hour over a small area. In Köppen's scheme the west coast is Amw, the Coromandel coast As and most of the Peninsula Aw. IMD (1875) forecasts the season against the long period average (LPA) of about 87 cm (1971–2020): normal is 96–104 per cent, deficient below 90 and excess above 110; the first forecast comes in mid-April.

Exam traps

Recap

Practice questions

Q1. Consider the following statements about the jet streams over India:
1. In winter the subtropical westerly jet flows south of the Himalaya.
2. The tropical easterly jet is present over the Peninsula throughout the winter.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct. Statement 2 is wrong: the tropical easterly jet appears only in the monsoon months. So '2 only' and 'both' are wrong, and 'neither' is wrong because statement 1 is true.

Q2. Under the normal dates revised by IMD in 2020, the south-west monsoon covers the whole of India by about:

  1. 1 June
  2. 15 June
  3. 8 July
  4. 15 July
Show answer

Answer: C. 8 July

The revised normal date is about 8 July. 1 June is the onset over Kerala; 15 June is not a normal date for covering the country; 15 July was the old date before the 2020 revision.

Q3. The winter rainfall of Punjab and Haryana, useful for the wheat crop, is caused mainly by:

  1. The retreating south-west monsoon
  2. Western disturbances
  3. North-east trade winds from the Bay of Bengal
  4. Kalbaisakhi storms
Show answer

Answer: B. Western disturbances

Western disturbances from the Mediterranean region, steered by the westerly jet, bring this winter rain. The retreating monsoon gives rain mainly to the south-east coast; north-east winds over the Bay give winter rain to Tamil Nadu; kalbaisakhi are hot-season storms of eastern India.

Q4. Match List I with List II:
List I (Local storm or shower) — List II (Region)
A. Kalbaisakhi — 1. Coffee areas of Karnataka
B. Mango showers — 2. West Bengal
C. Blossom showers — 3. Kerala coast
Select the correct answer using the code given below:

  1. A-2, B-3, C-1
  2. A-3, B-2, C-1
  3. A-2, B-1, C-3
  4. A-1, B-3, C-2
Show answer

Answer: A. A-2, B-3, C-1

Kalbaisakhi strikes West Bengal (A-2), mango showers fall on the Kerala coast (B-3) and blossom showers make coffee flower in Karnataka (C-1). Option (b) swaps kalbaisakhi and mango showers; (c) swaps the two kinds of shower; (d) puts kalbaisakhi in the coffee areas.

Q5. Which one of the following best explains why the Coromandel coast receives its main rainfall between October and December?

  1. Western disturbances reach the far south in these months
  2. North-easterly winds pick up moisture over the Bay of Bengal, aided by depressions and cyclones
  3. The Arabian Sea branch crosses the Western Ghats at full strength
  4. The ITCZ moves north over the Ganga plain
Show answer

Answer: B. North-easterly winds pick up moisture over the Bay of Bengal, aided by depressions and cyclones

The north-east monsoon winds gather moisture over the Bay and, with depressions and cyclones, bring rain to Tamil Nadu. Western disturbances affect the north-west; the Arabian Sea branch is a June–September feature and leaves this coast in rain shadow; the ITCZ is over the Ganga plain in July, not in October–December.

Q6. Consider the following statements about tropical cyclones affecting India:
1. The main cyclone season is October to December.
2. The Arabian Sea produces more cyclones than the Bay of Bengal.
Which of the statements given above is/are correct?

  1. 1 only
  2. 2 only
  3. Both 1 and 2
  4. Neither 1 nor 2
Show answer

Answer: A. 1 only

Statement 1 is correct. Statement 2 is wrong: the Bay of Bengal produces far more cyclones. So '2 only' and 'both' are wrong, and 'neither' is wrong because statement 1 is true.

Q7. Which one of the following regions has both low annual rainfall and the least reliable rainfall in India?

  1. Western Rajasthan
  2. Meghalaya
  3. Konkan coast
  4. Lower Ganga plain
Show answer

Answer: A. Western Rajasthan

Western Rajasthan gets under 50 cm and has a coefficient of variation above 50 per cent. Meghalaya, the Konkan coast and the lower Ganga plain all receive heavy rain with low variability.

Q8. IMD classifies a south-west monsoon season as 'normal' when all-India rainfall is:

  1. 90 to 110 per cent of the LPA
  2. 96 to 104 per cent of the LPA
  3. 100 per cent of the LPA exactly
  4. Above 110 per cent of the LPA
Show answer

Answer: B. 96 to 104 per cent of the LPA

Normal is 96–104 per cent of the LPA. 90–110 per cent mixes in the below-normal and above-normal bands; an exact 100 per cent is too narrow to be a category; above 110 per cent is 'excess'.

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