Chennai rain red alert: IMD warns of extremely heavy rain after the city's 36 cm night

Short answer: Yes, Chennai is on red alert. The Regional Meteorological Centre in Chennai has forecast extremely heavy rainfall, above 20 cm, for the city in the 24 hours from Sunday afternoon (18 October), PTI reported at 5:02 PM IST. Six other districts are on orange alert. It comes less than a day after the northeast monsoon's first big spell dumped 36 cm at Parry's Corner overnight, the city's heaviest rain since Cyclone Michaung in December 2023.

What the red alert means

IMD's colour codes are about expected rainfall, not damage already done:

A red alert is IMD's signal to take action: avoid low-lying roads and subways during downpours, keep phones charged, and don't plan non-essential travel during the heaviest hours. It does not by itself close schools or offices; that is for the district collector or the state government to order.

What happened on Saturday night

The rain began around 6 PM on Saturday in north Chennai and spread across the city with heavy thunder and lightning, running until about 1:30 AM, according to ETV Bharat. IMD's 24-hour figures to 8:30 AM Sunday:

• Parry's Corner (Chennai): 36 cm
• Kathivakkam (Chennai): 34 cm
• Greater Chennai Corporation said six areas crossed 20 cm and 12 areas crossed 11.5 cm.

Weather blogger Pradeep John (Tamil Nadu Weatherman) called it the heaviest rain Chennai has seen since Cyclone Michaung in December 2023, coming after nearly 25 dry days. RMC Chennai said the downpour could be described as a localised cloudburst, caused by a cyclonic circulation over north Tamil Nadu and south coastal Andhra Pradesh. That circulation has since become less marked, but the monsoon remains vigorous.

Airport, roads and relief

• Flights: more than 20 flights were affected at Chennai airport. An IndiGo flight from Kolkata was diverted to Hyderabad, over 10 arrivals were held in the air, and departures to Singapore, Kuala Lumpur, Abu Dhabi, Delhi, Mumbai and others were delayed (ETV Bharat, Mathrubhumi).
• Roads and subways: the Corporation said all 22 subways were cleared and open by 6 AM Sunday, and water had been cleared from all major bus routes, with pumping continuing in a few low-lying pockets. The Kilambakkam bus terminus was waterlogged overnight.
• Relief: 9 relief centres were opened, and one NDRF and four TNDRF teams were deployed. The Corporation reported no casualties from the overnight rain.
• Helpline: residents can report waterlogging on the GCC helpline 1913.

Is Monday a holiday?

Schools in Tamil Nadu are already shut on Monday, 19 October for Ayudha Pooja / Saraswati Pooja, and on Tuesday, 20 October for Vijayadashami, under the state's school calendar. That is a scheduled holiday, not a rain holiday. If the red alert continues into later in the week, watch the Chennai district collector's announcements for any rain-related closures.

What IMD expects next

IMD's national bulletin (1:30 PM IST, 18 October) says the wet spell will continue over Tamil Nadu, Puducherry and Karaikal till 24 October, with isolated very heavy rain likely till 21 October and thunderstorms with gusty winds of 40–50 km/h possible. RMC Chennai's district forecast keeps Chennai under heavy to very heavy rain warnings into Monday, with heavy rain possible again midweek.