PrepMaticTamil Nadu GK · Geography & nature
Climate and monsoon of Tamil Nadu: seasons, rainfall and cyclones
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Tamil Nadu has a tropical climate with a hot summer, mild winter and two monsoons, and unlike most of India it gets the largest share of its rain from the north-east monsoon between October and December. The state lies in the rain shadow of the Western Ghats during the south-west monsoon, so the plains are comparatively dry from June to September. The numbers below are approximate, but the pattern is what questions test.
The four seasons
The India Meteorological Department (IMD) divides the year into four seasons, and the calendar below applies to Tamil Nadu.
| Season | Months | What happens in Tamil Nadu |
|---|---|---|
| Winter (cold weather) | January to February | Cool and dry; temperatures fall in the hills; some coastal showers |
| Summer (hot weather) | March to May | Hottest period, especially in the interior, with highs in May; thunderstorms in the evenings |
| South-west monsoon | June to September | Heavy rain on the Western Ghats and Nilgiris; the plains are dry, apart from Courtallam and Kanniyakumari |
| North-east monsoon | October to December | Main rainy season; heavy rain on the coast and delta; cyclones from the Bay of Bengal |
The hottest days around May are traditionally called Agni Natchathiram or Kathiri Veyil in Tamil, a term that regularly appears in cultural questions.
Why the north-east monsoon matters most
The north-east monsoon brings roughly half of Tamil Nadu's annual rainfall, with the south-west monsoon contributing about a third of the total; the shares vary by the normal used. It begins around mid-October, when winds from the north-east pick up moisture over the Bay of Bengal and bring it onto the Coromandel coast. Cuddalore, Mayiladuthurai, Nagapattinam, Thiruvarur, Thanjavur and Chennai receive the strongest rain. Because paddy in the Cauvery delta depends on it, a weak north-east monsoon hits the Samba and Thaladi crops. Read more on major crops of Tamil Nadu.
Rain shadow and regional differences
- Wettest. The Western Ghats slopes of the Nilgiris, Valparai and Kanniyakumari receive the heaviest rain, mainly from the south-west monsoon. Kanniyakumari also gets rain in the north-east monsoon, so it has two rainy seasons.
- Driest. The plains of Ramanathapuram, Thoothukudi, Tirunelveli and the inland south-east receive less rain and often face drought.
- Delta and coast. Mostly north-east monsoon rain.
- Courtallam exception. The Shencottah gap lets some south-west rain reach the Courtallam area, giving it a waterfall season in June to September.
- Hills. Ooty and Kodaikanal stay cool all year, and temperatures drop sharply in December and January.
Cyclones and floods
Cyclones in the Bay of Bengal form mainly in October to December and are a major hazard on the Tamil Nadu coast. Notable ones include Thane (2011, Cuddalore), Vardah (2016, Chennai), Gaja (2018, Nagapattinam and Vedaranyam), Nivar (2020, near Puducherry), Michaung (2023, which flooded Chennai) and Fengal (2024, near Puducherry). The 2015 Chennai floods were driven by exceptionally heavy north-east monsoon rain and reservoir releases on the Adyar. Disaster management for the state falls under the Tamil Nadu State Disaster Management Authority. For the broader syllabus topic, see the TNPSC geography guide.
Short notes on most-asked items
- Season names. Cold weather, hot weather, south-west monsoon and north-east (retreating) monsoon.
- Main rain. North-east monsoon, October to December.
- Rain shadow. Created by the Western Ghats during the south-west monsoon.
- Cyclone season. Mainly October to December.
- Heat. May is the hottest month in most of the interior, but exact records change; ask for the year before quoting a figure.
- Tamil seasons. The traditional six seasons are Ilavenil, Mudhuvenil, Kaar, Koothir, Munpani and Pinpani. Questions on Sangam literature use this system.
How to revise
Memorise the four seasons by month, then tie each to a region: the south-west monsoon with the Ghats and Kanniyakumari, the north-east monsoon with the coast and delta, summer with the interior, winter with the hills. Then match the cyclone names to years. The rivers of Tamil Nadu page explains why many rivers are seasonal, and the soils of Tamil Nadu page explains how rainfall shapes cropping.
Frequently asked questions
Which monsoon gives Tamil Nadu the most rain?
The north-east monsoon, from October to December, gives the largest share of the state's annual rainfall.
Why is Tamil Nadu dry during the south-west monsoon?
The Western Ghats block the moisture-laden south-west winds, and the plains lie in their rain shadow.
Which are the four seasons used by IMD in Tamil Nadu?
Winter (January to February), summer (March to May), south-west monsoon (June to September) and north-east monsoon (October to December).
What is Agni Natchathiram?
The hottest period of the Tamil year, around May, also called Kathiri Veyil.
Official sources
Rainfall normals are revised by IMD from time to time, so use their latest data when a question asks for numbers.
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