Heavy rain alert for 21 Tamil Nadu districts; Chennai thunderstorms likely
Synopsis
A low-pressure system over the northern Andaman Sea is pushing heavy rain into 21 Tamil Nadu districts on 21 September, with Chennai bracing for thunderstorms. Moderate rain is also on the cards for the northern coastal belt on 23 and 24 September, and district administrations have been told to keep emergency response teams on standby.
Key Takeaways
The Regional Meteorological Centre has issued a heavy rain forecast for 21 Tamil Nadu districts on 21 September .
A low-pressure area over the northern Andaman Sea is driving the weather system.
Chennai is likely to receive light to moderate rain with thunderstorms and lightning on Monday.
Moderate rain is forecast for Chennai, Tiruvallur, Kancheepuram, Chengalpattu and Ranipet on 23 and 24 September .
Fishermen , motorists and residents in low-lying areas have been advised to monitor official alerts and exercise caution.
Civic authorities have been directed to clear stormwater drains and keep pumping equipment ready in flood-prone zones.
The Regional Meteorological Centre (RMC) has forecast heavy rainfall across 21 districts of Tamil Nadu on Monday, 21 September, as a low-pressure area over the northern Andaman Sea continues to drive moisture-laden winds into the state. Chennai is also on alert for light to moderate rain accompanied by thunderstorms and lightning through the day.
Districts Under Heavy Rain Alert
Heavy rain is likely at isolated places in the Nilgiris, Coimbatore, Dharmapuri, Krishnagiri, Dindigul, Pudukkottai, Tiruvarur, Nagapattinam, Mayiladuthurai, Perambalur, Ariyalur, Kallakurichi, Villupuram, and Tiruvannamalai. Similar conditions are expected across Sivaganga, Thanjavur, Madurai, Cuddalore, Tirupattur, Vellore, and Tiruchirappalli.
What the Weather System Is Doing
The low-pressure system formed over the northern Andaman Sea is channelling widespread moisture into several parts of Tamil Nadu, with some districts likely to experience short but intense spells. The weather department noted that rainfall intensity could vary significantly from one location to another. On Tuesday, light to moderate rain is expected at a few places in districts along the Western Ghats, as cloudy conditions and intermittent showers persist in interior and coastal areas while the system moves further.
Chennai and Northern Coastal Belt
The sky over Chennai is expected to remain partly cloudy, with one or two areas in the city and its suburbs likely to see sudden showers accompanied by thunderstorms. Moderate rain has also been forecast for Chennai, Tiruvallur, Kancheepuram, Chengalpattu, and Ranipet districts on 23 and 24 September. The showers are expected to provide some relief from the prevailing humid conditions along the northern coastal belt.
Advisories and Precautionary Measures
Residents in vulnerable and low-lying areas have been advised to remain cautious, particularly during intense rainfall spells. Fishermen and people living near waterbodies have been urged to monitor official weather updates closely. Motorists have been cautioned about the risk of waterlogging and reduced road visibility. Civic authorities have been directed to ensure stormwater drains remain clear and that pumping equipment is on standby in flood-prone zones. The public has also been warned against taking shelter beneath trees or near weak structures during thunderstorms. District administrations are expected to keep emergency response teams on alert should the rainfall intensify.
Point of View
Including perennially flood-prone Chennai, has struggled to keep pace with recurring inundation. The RMC's advisory is sound, but the real test lies in whether district administrations translate the alert into timely drain-clearing, pumping deployment and public communication — steps that historically arrive too late. The 23-24 September extension of the forecast also means this is not a one-day watch; preparedness needs to hold across several days.
NationPress
21 Sept 2026
Frequently Asked Questions
Which Tamil Nadu districts are under heavy rain alert on 21 September?
The Regional Meteorological Centre has forecast heavy rainfall in 21 districts, including the Nilgiris, Coimbatore, Dharmapuri, Krishnagiri, Dindigul, Pudukkottai, Tiruvarur, Nagapattinam, Mayiladuthurai, Perambalur, Ariyalur, Kallakurichi, Villupuram, Tiruvannamalai, Sivaganga, Thanjavur, Madurai, Cuddalore, Tirupattur, Vellore, and Tiruchirappalli. Intensity may vary from one location to another.
Why is it raining heavily in Tamil Nadu right now?
A low-pressure area formed over the northern Andaman Sea is channelling moisture-laden winds into Tamil Nadu, triggering widespread rainfall. Such systems are a common driver of heavy rain in the state, particularly during the northeast monsoon transition period.
Will Chennai be affected by the rain on 21 September?
Yes. Chennai is expected to receive light to moderate rain with thunderstorms and lightning on Monday. The sky will remain partly cloudy, and one or two areas in the city and its suburbs may see sudden heavy showers.
When will the rains ease in Tamil Nadu?
The weather department has indicated that light to moderate rain will continue along the Western Ghats on Tuesday, with intermittent showers persisting in interior and coastal areas. Moderate rain is also forecast for Chennai and nearby districts on 23 and 24 September, suggesting the system will influence weather for several days.
What precautions have authorities issued for Tamil Nadu residents?
Residents in low-lying areas have been urged to stay cautious during intense spells. Fishermen have been told to monitor weather updates closely, motorists have been warned about waterlogging and poor visibility, and the public has been advised not to shelter under trees or near weak structures during thunderstorms. District administrations have been directed to keep emergency response teams on standby.
