Tamil Nadu Weather: Heavy Rains in 25 Dists, 8 on Red Alert; Threatens To Dampen Diwali Sparkle

Updated: Tuesday, October 21, 2025, 17:35 [IST]

2025-10-21The Regional Meteorological Centre (RMC), Chennai, has issued alerts for widespread heavy rainfall across Tamil Nadu on Tuesday, warning that showers may disrupt Diwali festivities and cracker-bursting plans in several parts of the state.

According to the latest RMC bulletin, 25 districts are expected to receive heavy to very heavy rainfall. Of these, 8 districts are on red alert, 10 on orange alert, and 7 on yellow alert. The red alert - indicating extremely heavy rainfall - has been issued for Ramanathapuram, Pudukkottai, Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai, Cuddalore, and Villuppuram districts, as well as Puducherry and Karaikal.

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சென்னையில் உள்ள மண்டல வானிலை ஆய்வு மையம் (RMC), செவ்வாய்க்கிழமை அன்று தமிழ்நாடு முழுவதும் கனமழை பெய்யும் என எச்சரிக்கை விடுத்துள்ளது; மேலும், ராமநாதபுரம், புதுக்கோட்டை, தஞ்சாவூர், திருவாரூர் உட்பட 8 மாவட்டங்களுக்கு ரெட் அலர்ட் விடுக்கப்பட்டுள்ளது.

Tamil Nadu Weather Heavy Rains in 25 Districts 8 on Red Alert Threatens To Dampen Diwali Sparkle

The orange alert, suggesting heavy to very heavy rainfall, covers Ariyalur, Perambalur, Kallakurichi, Chengalpattu, Chennai, Tiruvallur, Kancheepuram, Thoothukudi, Tirunelveli, and Kanyakumari districts. Meanwhile, a yellow alert has been issued for Villuppuram, Chengalpattu, Cuddalore, Mayiladuthurai and adjoining Puducherry areas, warning of moderate to heavy rainfall activity.

Weather Systems Behind the Downpour

The RMC said that a Well Marked Low Pressure Area has formed over the Southwest Bay of Bengal, influenced by an upper air cyclonic circulation extending up to 7.6 km above mean sea level. The system is likely to move west-northwestwards and intensify into a depression over the Southwest and adjoining West-Central Bay of Bengal off the North Tamil Nadu and South Andhra Pradesh coasts by Tuesday afternoon (October 22).

It is expected to further strengthen and move towards the Tamil Nadu, Puducherry, and South Andhra Pradesh coasts, bringing widespread rains and strong winds over the next 48 hours.

Director, Regional Metrological Centre, Chennai, B Amudha said, "...Under the influence of an upper cyclonic circulation over the South Andaman Sea and the southeast Bay of Bengal, a low-pressure area has formed over the southwest Bay of Bengal at 5:30 hours IST today...It is likely to move northwestwards and concentrate into a depression over the southwest and adjoining west central Bay of Bengal of north Tamil Nadu and South Andhra coast by the afternoon of 22nd October, 2025.

There is an upper air cyclonic circulation over the South Andaman Sea and its neighbourhood, and it extends upto 5.8 km above our main sea level...Yesterday's well-marked low-pressure area over the southeast Arabian Sea persisted over the same region at 8:30 hours IST today...It is likely to move slowly westwards and concentrate into a depression during the next 24 hours. From the depression stage, it is likely to become a deep depression...For today and tomorrow, we have given an extremely heavy rainfall warning to the coastal districts of Tamil Nadu...Fishermen are advised not to venture into the sea from 21st to 25th..."

Meanwhile, another Well Marked Low Pressure Area over the Southeast Arabian Sea persists and is also expected to intensify into a depression within the next 24 hours. An upper air cyclonic circulation over the South Andaman Sea continues to influence the weather, while the earlier cyclonic circulation over South Kerala and Comorin area has weakened.

Chennai Weather Forecast

For Chennai, intermittent spells of moderate to heavy rain accompanied by thunderstorms and lightning are likely in some parts of the city. The maximum temperature is expected to hover around 28°C, while the minimum will remain between 24°C and 25°C, the RMC said.

Rainfall Highlights (as of Monday)

Several parts of Tamil Nadu recorded intense rainfall on Monday, with Thangachimadam (Ramanathapuram district) receiving the highest rainfall of 17 cm. It was followed by Pamban (15 cm), Mandapam (14 cm), Varattupallam (Erode, 13 cm), and Velankanni (Nagapattinam) and Annamalai Nagar (Cuddalore) with 10 cm each.