Chennai is likely to receive moderate to heavy rain, thunderstorms and lightning from Friday after the India Meteorological Department issued a yellow alert for rainfall of 6–12cm in 24 hours across the city and neighbouring districts over the next four days.
The warning follows light rain in parts of Chennai on Thursday night after a day of alternating sunshine and cloudy skies. The IMD has forecast heavy rain in 26 districts on Friday, including Chennai and Tiruvallur, as a low-pressure system over the southwest Bay of Bengal influences weather conditions across Tamil Nadu.
The low-pressure area has moved towards the Comorin region and adjoining parts of southern Tamil Nadu and Kerala. Its associated cyclonic circulation extends up to 5.8km above mean sea level, according to the report. The circulation is helping lift moist air, which cools and condenses to form rain-bearing clouds.
An IMD official said the system could move northwards, bringing rain to Chennai and surrounding areas. The agency expects the system and related atmospheric instability to sustain rainfall across several parts of the state.
For Chennai, the forecast indicates moderate to heavy rain along with thunderstorms and lightning on Friday. Cloud cover is expected to keep the maximum temperature between 31°C and 32°C, while the minimum temperature is likely to remain between 25°C and 26°C.
The alert coverage is expected to widen from October 24 to 26, when Chengelpet and Kancheepuram will join Chennai and Tiruvallur among the districts facing a heavy-rain warning. Several delta and interior districts are also included in the forecast for that period.
An orange alert for heavy to very heavy rain has been issued for districts along the Western Ghats from October 23 to 26. The contrasting alert levels reflect the spread of the weather system across Tamil Nadu, with heavier rainfall expected in parts of the Western Ghats while northern districts, including the Chennai region, remain under a yellow alert.
The latest warning places rainfall intensity, thunderstorms and lightning at the centre of the immediate weather risk for Chennai and its neighbouring urban districts. The IMD’s four-day forecast will remain the key official reference as the system moves northwards and the warning period progresses.
