Chennai, October 19, 2025: The Regional Meteorological Department has issued a warning of heavy rainfall in Tamil Nadu and Puducherry over the next 24 hours, as a low-pressure system is expected to form over the Southeast Bay of Bengal around October 21. The development comes after the onset of the North East Monsoon on October 16, which has already brought significant rainfall across the state.

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Rainfall Forecast and District-wise Details

• Tamil Nadu: Heavy rain is expected in the ghat areas of Coimbatore, Nilgiris, Erode, Tiruppur, Theni, and Tenkasi districts.
• Kerala: Some districts are likely to experience heavy rainfall, especially in the hilly regions.
• Chennai & Neighbourhood: Forecast predicts one or two spells of light to moderate rain, with thunderstorms and lightning possible in some areas.

According to the latest rainfall measurements:

• Kothagiri (Nilgiris) recorded the maximum rainfall at 14 cm in the last 24 hours.
• Sirkali (Mayiladuthurai) recorded the minimum rainfall at 1 cm.

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Meteorological Analysis

The Met department reported that an Upper Air Cyclonic circulation persists over the South Andaman Sea and adjoining Southeast Bay of Bengal, extending up to 1.5 km above sea level.

• This circulation is likely to lead to the formation of a low-pressure system over Southeast Bay of Bengal around October 21, 2025.
• The system is expected to move northwestwards and may intensify into a depression over central Bay of Bengal within 48 hours after formation.

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Wind and Sea Conditions

• Squally weather is likely over the South Tamil Nadu coast, Gulf of Mannar, and Comorin area, with wind speeds reaching 35–45 kmph, gusting up to 55 kmph.
• Fishermen advisory: Those in the deep sea of South Bay of Bengal and adjoining West-central Bay of Bengalare advised to return to the coast by the morning of October 21. Fishermen are warned not to venture into the sea due to rough conditions.

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Summary & Safety Measures

1. Heavy rainfall expected over Tamil Nadu and Puducherry; Kerala may also see significant rain.
2. Light to moderate rain with thunderstorms possible in Chennai.
3. Low-pressure system forming in Southeast Bay of Bengal around October 21, likely to intensify into a depression.
4. Squally winds and rough sea conditions expected; fishermen advised to exercise caution.

Residents in affected areas are advised to stay updated with weather alerts and take necessary precautions to avoid disruptions due to flooding, waterlogging, and strong winds.