Heavy rainfall batters Chennai as northeast monsoon brings rain fury, over 20 cm recorded in 24 hours

Chennai experienced an exceptionally intense burst of rain over 24 hours. Most parts of the city and nearby areas received more than 20 centimetres. Such totals can quickly overwhelm roads, drains, subways, and low-lying neighbourhoods, making the figures important for emergency planning and public safety.

Parrys recorded the highest amount, at 36.3 cm. Kathivakkam in North Chennai received 34 cm. Central Chennai recorded 27 cm, while Thiruvottiyur and Ennore each received 22 cm. MGR Nagar recorded 19 cm. Twelve other city locations received more than 11.5 cm.

The Regional Meteorological Centre said the northeast monsoon remained active. Despite the rainfall, the government reported no major accident or loss of life during the previous 24 hours. Relief teams continued pumping water from inundated streets, subways, and low-lying areas, while forecasts warned of further heavy rain in several districts.

The northeast monsoon is a seasonal wind and rainfall pattern that brings important rain to southeastern India. It is especially significant for Tamil Nadu and Puducherry. The article says the season officially sets in between October and December every year. This timing matters because communities, authorities, and weather services prepare for concentrated rainfall and possible flooding.

During the reported event, the Regional Meteorological Centre said the northeast monsoon remained active across the region. Chennai and adjoining areas received extremely heavy rain, with many places recording more than 20 centimetres in 24 hours. Parrys recorded 36.3 centimetres, the highest reported total.

The monsoon also shaped the forecast beyond Chennai. Heavy rain was expected in several Tamil Nadu districts, with thunderstorms and lightning possible. Moderate rain was forecast across the rest of Tamil Nadu and Karaikal. Officials therefore issued safety advice and kept disaster-response resources ready.

An upper-air cyclonic circulation is a region of counterclockwise, organised air movement around lower pressure in the atmosphere. It does not necessarily mean a fully formed cyclone. The article linked Chennai’s heavy rainfall to such a circulation over north Tamil Nadu and adjoining south Coastal Andhra Pradesh, between 4.5 and 5.8 kilometres above sea level.

This kind of circulation can encourage moist air to converge and rise. As the air rises, it cools, and water vapour condenses into clouds. If the moisture supply is strong and the rising motion persists, the clouds can produce intense or prolonged rain. Thunderstorms and lightning may occur as well.

In this case, the circulation was present while the northeast monsoon was active. The result was extremely heavy rain across Chennai and nearby areas. The forecast also warned of heavy rain, thunderstorms, and lightning in several Tamil Nadu districts, showing that the weather system affected a broad region.

Waterlogging and flooding occur when rain falls faster than drains, channels, and pumps can carry it away. Chennai received extremely heavy rainfall across much of the city, with more than 20 centimetres recorded in many areas during 24 hours. That sudden volume created a major runoff burden for streets and drainage infrastructure.

The impact was especially visible in low-lying areas, where water naturally collects. Subways also became flooded because they sit below surrounding road levels. The government said water was pumped out of the subways and that traffic movement had been restored. Rainwater was cleared from major arterial roads and much of the street-level stagnation.

However, efforts continued in low-lying areas, showing that the problem was not immediately over. Nearly 650 electric and tractor-mounted pumps were deployed. The response reduced standing water, while nine relief centres supported affected residents. Further forecasts meant officials still had to prepare for additional flooding.

The Tamil Nadu government directed senior ministers, lawmakers, and officials to lead relief and rehabilitation work in affected locations. This involved clearing water, supporting residents, monitoring vulnerable areas, and coordinating emergency operations. The government also reported that major roads and many streets had been cleared, although work continued in low-lying areas.

Nearly 15,000 conservancy staff were engaged. Around 650 electric motor pumps and tractor-mounted pumps were used to remove water from inundated areas. Water was pumped out of subways, restoring traffic movement. Nine relief centres were also established for people affected by the downpour.

The National Disaster Response Force was brought in for rehabilitation work in flood-prone areas. Four State Disaster Response Force teams were kept on standby, ready for further deployment. This layered response mattered because forecasts still warned of heavy rain, thunderstorms, and lightning across Chennai and several other Tamil Nadu districts.

Extreme rainfall becomes less dangerous when water is removed quickly and people receive clear instructions. Pumps can shift water from flooded streets, subways, and low-lying areas. Drainage systems carry runoff away from roads and neighbourhoods. Relief centres give affected residents a safer place to go and make organised assistance easier.

Chennai used nearly 650 electric motor pumps and tractor-mounted pumps. Officials said water was pumped from subways, restoring traffic movement. Major arterial roads and many streets were cleared, though work continued in low-lying areas. The government also opened nine relief centres for people affected by the rain.

Public warnings reduce risk before conditions worsen. The TNSDMA sent a flash SMS asking people to stay safe, follow official forecasts, and follow safety guidance. This was important because more heavy rain, thunderstorms, and lightning were forecast. These measures cannot stop rainfall, but they can reduce flooding’s effects and help residents respond sooner.

The northeast monsoon is important to Chennai because seasonal winds bring moist air toward Tamil Nadu during the October–December period. The article states that Tamil Nadu and Puducherry usually receive rainfall during this season. In general, winds moving across the Bay of Bengal gather moisture before reaching the southeastern coast, making the bay central to the region’s rain supply.

When this moist air converges and rises, clouds develop and can produce heavy showers. Weather disturbances over the Bay of Bengal or nearby land can strengthen that process. In this event, the Regional Meteorological Centre identified an upper-air cyclonic circulation over north Tamil Nadu and adjoining south Coastal Andhra Pradesh, 4.5 to 5.8 kilometres above sea level.

The active monsoon and circulation produced extreme rainfall in Chennai. Parrys recorded 36.3 centimetres in 24 hours. Because the monsoon can bring further rain, officials continued pumping water, operating relief centres, and issuing warnings as forecasts covered several districts.