North coastal districts are likely to continue experiencing evening thundershowers this week due to wind convergence. The Regional Meteorological Centre (RMC) has forecast isolated heavy rainfall in various parts of north coastal Tamil Nadu over the next two days.

Daily spells of rain have become a feature of August weather in Tamil Nadu. Wet weather bringing rainfall of light to moderate intensity is likely in other parts of the State, particularly the Western Ghats region, till August 23.

According to the RMC, heavy rainfall is likely with gusty winds reaching a speed of 40-50 kmph at one or two places over Chengalpattu and Villupuram districts on Tuesday. A few other places in north coastal Tamil Nadu, Puducherry, and Karaikal may receive moderate rainfall on both Tuesday and Wednesday.

On Wednesday, isolated heavy rainfall might cover more districts- Nilgiris, Chennai, Chengalpattu, Tiruvallur, and Villupuram. Some places may experience light rainfall with thundershower activity throughout the week.

V.R. Durai, Head, Regional Weather Forecasting Centre, RMC, said a depression over the north Bay of Bengal would trigger wind convergence and sustain the wet spell, particularly over north coastal Tamil Nadu this week.

However, interior places like Tiruchi, Madurai, and Karur, may experience sweltering heat as moisture incursion would not penetrate far inland.

Though coastal places like Chennai experience relatively above normal temperatures, the onset of sea breeze in the evening helps keep temperatures in check, he said.

Scattered rainfall across various parts of the State since the start of August has kept the overall rainfall deficit within the normal range for this season. On Monday, places like Puzhal and Madhavaram in Chennai (1 cm each), Coimbatore and Kanniyakumari districts recorded light rainfall till 6 p.m.

The India Meteorological Department has also invited citizens to give their feedback online (https://mausam.imd.gov.in/survey_app/survey.php?survey=hw_gp) on the usefulness of heatwave alerts. The feedback link would be open till September 13 to register responses.

A few days into July, many places, particularly the coastal region, continue to sizzle with higher temperatures as the Southwest monsoon remains subdued over the State. With rainfall expected to be largely confined to the Western Ghats region till July 13, dry weather may prevail over most parts of the State.

For the past three days, coastal places, along with a few interior areas, have been experiencing hot weather. The mercury level remained six degrees Celsius above normal in Thondi in Ramanathapuram district for three consecutive days and was also hottest weather station in the State. The maximum temperature peaked at 40.7 degrees Celsius in Thondi on Monday, which was the hottest July temperature recorded there in the past decade. On Tuesday, Thondi, again, registered the highest day temperature of 40.3 degrees Celsius in the State.

Chennai has been experiencing elevated day temperatures and hot afternoons since the start of the week. While Nungambakkam recorded its maximum temperature of 38.9 degrees Celsius, Meenambakkam also registered 39 degrees Celsius on Tuesday.

The Regional Meteorological Centre (RMC) has forecast light rainfall in one or two places in the State, Puducherry, and Karaikal areas during the next week. However, isolated places in Western Ghats districts like Coimbatore and Nilgiris may experience showers of light to moderate intensity.

Officials of the RMC said while the monsoon has gained strength in other parts of the country, including central India, its activity has turned subdued over Tamil Nadu. The prevailing strong westerly, southwesterly winds have delayed the onset of sea breeze, depriving many coastal places of the usual afternoon relief and contributing to rising heat levels.

V.R. Durai, Head, Regional Weather Forecasting Centre, RMC said the lack of widespread rainfall is expected to keep daytime temperatures slightly above normal, prolonging the warm spell in July. Noting that coastal places like Thondi experienced relatively unusual day temperatures, he said the delayed onset of sea breeze in coastal places like Thondi, Nagapattinam, and Chennai, kept the day temperature elevated.

On Tuesday, heat remained unrelenting in Chennai as the mercury level hovered around 37 degrees Celsius, even at 4.30 p.m. Strong southwesterly winds prevented wind convergence and possibility of cloud formation. However, the wind pattern is likely to change towards the weekend, bringing some respite to the State.

The RMC has forecast that Chennai might record a maximum temperature of 37-38 degrees Celsius on Wednesday.

After a spell of soaring temperatures this June, Chennai and its fringes will experience cool weather on Saturday (June 20, 2026), with strong northeasterly winds bringing in moisture.

The mercury level in the city was around 32 degree Celsius at 10 a.m. on Saturday, much lower than its average temperature of 37 degree Celsius recorded in June. However, humidity level was high at 75%.

This was much lower than the day temperature of 37.9 degree Celsius recorded in Chennai on Friday (June 19). Palayamkottai had registered a hottest temperature of 39 degree Celsius in the State on Friday.

The Regional Meteorological Centre (RMC) has said that a broad cloud band located about 80-100 km east-northeast of Chennai over the Bay of Bengal is likely to increase cloud cover across the city and suburbs. Humidity level would also see a spike.

Chennai may be spared soaring temperatures as daytime temperatures would remain one to three degree Celsius below normal due to reduced sunshine. Stronger sea breeze would help sustain moist onshore winds.

Possibility of thundershowers

Though widespread heavy rainfall may not be possible, north coastal areas, including Chennai, will experience light to moderate thundershowers in isolated areas. The city may enjoy a cloudier, slightly cooler but more humid weather on Saturday. However, the RMC has noted no major rainfall event is expected in Chennai for the day.

During the past 24 hours ending 8.30 a.m. on Saturday, Aavoor in Thiruvarur district received heavy rainfall of 14 cm, which was the highest rainfall recorded in the State. Various other weather stations in delta and interior districts too received moderate to heavy rainfall.

In its Nowcast valid till 1 p.m. on June 20, the RMC has predicted light to moderate rainfall with thunderstorms and lightning in districts, including Chennai, Kancheepuram, Vellore, Ranipet, Tiruvallur, Pudukottai, Erode, and Villupuram. Rainfall may affect traffic in some areas and also cause waterlogging, the RMC has said.

After pilot projects in a city government school and a Perumbakkam housing complex showed that cool roof coatings could lower indoor temperatures by up to 5°C during peak summer, the Tamil Nadu government on Thursday (June 4, 2026) released a State-level standard operating procedure (SOP) to scale up the intervention across homes, schools, and public buildings.

Launched on June 5, marking World Environment Day, the SOP is intended to standardise the implementation of cool roof coatings, which is a passive cooling measure that reflects solar radiation and reduces heat absorption by building surfaces. The document was released by Environment and Climate Change Minister V.K. Rajeev and Forests Minister R.V. Ranjithkumar.

Developed by the Tamil Nadu Green Climate Company (TNGCC) and the Tamil Nadu Climate Change Mission (TNCCM) in collaboration with the United Nations Environment Programme (UNEP) and Seeds Technical Services, the SOP lays down procedures for roof assessment, surface preparation, coating application, quality control, safety, and maintenance.

According to the government, a pilot project at the Perunthalaivar Kamarajar Government Girls Higher Secondary School in Ambattur reportedly reduced classroom temperatures from around 31-32°C to 26-28°C. Indoor air and ceiling surface temperatures fell by about 4°C to 5°C, helping classrooms remain within acceptable thermal comfort levels during school hours, the SOP says.

The SOP also cites a pilot intervention at the resettlement site in Perumbakkam, where cool roof coatings were applied over about 1,000 sq. m of roof area covering 120 housing units. The project recorded roof surface temperatures that were 6°C to 8°C lower than conventional roofs and indoor temperatures that were lower by 4°C to 5°C during peak summer months.

Officials said the Perumbakkam intervention also resulted in a 20% reduction in cooling energy demand and nearly 30% fewer thermal discomfort hours.

Reducing AC dependence

The SOP says that roofs are among the largest contributors to indoor heat gain in hot and humid regions and that reflective coatings can significantly improve thermal comfort while reducing dependence on air-conditioning and other mechanical cooling systems.

The document prescribes a 12-stage implementation framework covering feasibility assessment, material procurement, roof preparation, patch testing, primer application, coating, quality assurance, and periodic maintenance. It also recommends the use of high solar-reflective coatings and outlines technical specifications for procurement and implementation.

Environment, Climate Change, and Forests Secretary Supriya Sahu said the SOP would serve as the implementation framework for larger cool roof programmes in the State and could act as a model for other States looking to improve heat resilience while reducing energy demand and emissions.

The Regional Meteorological Centre, Chennai, said that the well-marked low-pressure area over the southwest Bay of Bengal recurved northeastwards gradually and lay over the same region at 5.30 p.m. on Sunday.

It is very likely to continue to move further northeastwards over southwest Bay of Bengal during the next 36 hours.

It is expected to bring light to moderate rain at isolated places in Western Ghat districts.

The RMC has forecast dry weather over the rest of Tamil Nadu, and Puducherry and Karaikal area on Monday and Tuesday.

Mist to prevail

Mist or haze is likely to prevail in isolated pockets of Salem, Dharmapuri, Krishnagiri, Tirupattur, Vellore, Ranipet, Tiruvallur, Chennai, and Kancheepuram in the early morning hours of Monday and Tuesday.

On Sunday, rainfall occurred at isolated places over the State (at a few places over south coastal Tamil Nadu and at isolated places over rest of the State), while dry weather prevailed over Puducherry and Karaikal area.