The Regional Meteorological Centre has forecast heavy rain with thunderstorms and gusty winds across 15 districts of Tamil Nadu on Sunday, 21 September and Monday, 22 September 2026, with Chennai expected to receive moderate thundershowers during the evening or night. The warning covers a broad swathe of the state, from the Nilgiris in the west to coastal districts in the east, along with the union territory of Puducherry.

Weather System Driving the Rain

A north-south trough extending from coastal Andhra Pradesh to the Gulf of Mannar, passing through parts of Tamil Nadu at approximately 0.9 km above sea level, is the primary system influencing conditions across the region. This kind of low-level trough typically draws moisture from the Bay of Bengal and the Arabian Sea, intensifying convective activity and triggering localised heavy spells.

Districts Under Heavy Rain Warning

Isolated heavy rain accompanied by thunderstorms, lightning, and gusty winds of 40–50 kmph is forecast for the Nilgiris, Coimbatore, Cuddalore, Krishnagiri, Salem, Tirupattur, Dharmapuri, Tiruvannamalai, Villupuram, Kallakurichi, Vellore, Perambalur, Ariyalur, Tiruchirappalli and Madurai districts. Puducherry may also experience similar conditions on both days.

Moderate thunderstorms are additionally forecast over remaining Western Ghats districts and a second tier of districts including Chennai, Kancheepuram, Chengalpattu, Tiruvallur, Sivaganga, Erode, Ramanathapuram, Namakkal, Mayiladuthurai, Thanjavur, Tiruvarur, Karur, Pudukottai, Nagapattinam and Karaikal. Light thundershowers remain possible elsewhere in the state.

Chennai Outlook and Temperatures

In Chennai and its suburbs, the sky will remain partly cloudy, with light to moderate rain and thunderstorms likely at a few places during the evening or night on Sunday. The maximum temperature is expected to range between 36°C and 37°C, while the minimum is likely to stay between 26°C and 27°C. Maximum temperatures are not expected to change significantly until 23 September and should remain close to seasonal norms.

Outlook for September 22–25

On 22 September, moderate to heavy rain may occur at isolated places across the Western Ghats districts and several coastal and interior districts, including Chennai and Madurai, with gusty winds of 40–50 kmph also likely. From 23 to 25 September, light to moderate rain is expected across the Western Ghats and northern coastal districts as the system gradually weakens.

Sea Warning for Fishermen

The meteorological centre has advised fishermen not to venture into the sea in notified areas. Squally winds of 45–55 kmph, occasionally reaching 65 kmph, are forecast over the Gulf of Mannar, adjoining Comorin area, and the southern Tamil Nadu coast on Monday. Winds are expected to strengthen further over parts of the Bay of Bengal on 22 and 23 September, reaching 50–60 kmph and occasionally 70 kmph. Residents and coastal communities are urged to stay alert to official updates as conditions evolve.