Heavy Rainfall For Chennai: Relief Next Week

Key Takeaways:

• Chennai has recorded 229.2 mm of October rainfall against the monthly normal of 300.3 mm.
• Heavy rainfall is expected across Chennai and its suburbs from October 19 to 21.
• Very heavy, short-duration showers are likely in parts of Chennai on October 20 and 21.
• Rainfall will ease after October 22, with a broader break expected from October 25.
• Forecast Validity: Next one week.

With the onset of the Northeast Monsoon on 15th October 2026, the state of Tamil Nadu as a whole, and the capital city Chennai in particular, have been receiving fairly widespread rainfall with isolated heavy spells. The Northeast Monsoon is the main rainy season for the state. October and November are the rainiest months, with normal rainfall exceeding 300 mm in each month.

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The regional observatory at Nungambakkam and the airport observatory at Minambakkam recorded 158 mm and 147 mm of rainfall, respectively, on the morning of 18th October. The city has accumulated 229.2 mm of rainfall so far this month against the normal of 300.3 mm. The shortfall is likely to be covered during this week itself.

There is a well-marked cyclonic circulation over the Southwest Bay of Bengal, off the Tamil Nadu coast, extending up to mid-tropospheric levels. A north-south trough is marked from the circulation to the Northwest Bay of Bengal in the lower levels. The seasonal northeasterly flow is quite strong over the central and western parts of the Bay of Bengal.

Under the combined influence of these systems, the entire coastal region of Tamil Nadu will generally experience fairly widespread moderate rain and thundershowers. The capital city, Chennai, is expected to receive heavy rainfall initially, which will taper to moderate intensity after mid-week.

Heavy rainfall across the city and suburbs is likely between 19th and 21st October, while moderate showers are expected between 22nd and 24th October. The peak intensity is likely on 20th and 21st October, when very heavy and short bursts of monsoon showers are expected over some parts of the city.

As the cyclonic circulation moves eastward, the northeasterly stream will flatten, reducing the spread and intensity of rainfall between 22nd and 23rd October. The remnant effect may still bring light rainfall over and around the city on 24th October 2026.

A broad clearance is likely from 25th October onwards. This break will last for at least four days. Another active system is likely to develop towards the end of the month over the Andaman Sea. This could revive monsoon activity around the beginning of next month.

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