For Tamil Nadu, peak summer traditionally ends in May. But this season, temperatures hovering around 40 degrees Celsius in several districts extended the searing conditions well into June, leaving residents grappling with exhausting days and uncomfortable, warm nights. Clearly, the time has come to go beyond seasonal, templated responses. It is against this backdrop that the State has recently rolled out its Heat Action Plan 2026, introducing measures such as local heat vulnerability mapping, early warning systems, and targeted interventions for vulnerable communities. At the same time, meteorologists are closely monitoring the tropical Pacific for strengthening of El Nino, which could influence weather patterns, rainfall, and heat risks in the months ahead. From outdoor workers and children to the elderly in dense urban neighbourhoods, rising temperatures and heat stress are a true test of endurance for all.

Spending most of his day navigating Chennai’s roads to complete deliveries, Selvam, a platform-based gig worker, says access to drinking water remains a challenge. “I am wary of drinking water from public kiosks so I carry a water bottle, but it gets over within an hour. I either request to refill it at places where I make deliveries or rely on buttermilk that residents and temples distribute,” he said.

Meteorologists said May 2026 was significantly warmer than normal across many parts of Tamil Nadu and among the hotter recent Mays, with inland areas experiencing persistent heatwave-like conditions. The observations of the Regional Meteorological Centre (RMC) indicate Vellore recorded the season’s hottest temperature of 42.5 degrees Celsius on May 22, followed by Tiruttani and Meenambakkam in Chennai. With temperatures peaking above the 40-degree mark during May’s last fortnight, persistent heat spell resulted in moderate to severe heat-stress and increased discomfort across many districts. RMC officials observed that the hot weather was driven by strong pre-monsoon solar heating, dry continental air prevailing over interior parts, and the delay in widespread southwest monsoon activity. Urban heat island (UHI) effect further intensified temperatures in densely populated areas.

Vulnerable interior districts

While factors such as inland location, limited influence of sea breeze, and semi-arid conditions make north interior and central interior districts most vulnerable to heat stress, the coastal urban Chennai Metropolitan Area (CMA) faces a different heat-related challenge owing to high humidity and UHI effect. A temperature of 37 degrees Celsius with high humidity can be more stressful to the human body than 40 degrees Celsius under dry conditions. Other meteorological factors, including cloud cover, rising humidity and wind patterns, played a role in warm nights in coastal places.

Pointing out that heatwave-like conditions have become more frequent, longer-lasting, and intense over the past decade in line with trends across India, V.R. Durai, Director, Regional Weather Forecasting Centre, RMC, says hot weather spells are becoming persistent with consecutive days of 40-degree-mark temperatures occurring often in interior districts such as Salem, Erode, Tiruchi, and Madurai.

Y.E.A. Raj, former Deputy Director-General of Meteorology, RMC, attributes the persistent heat in Tamil Nadu during June to strong westerlies and reduced monsoon clouding, leading to high temperatures that did not fall appreciably at night hours too at many places. The rain-shadow State tends to experience intense heat when thundercloud activity is absent. Heat stress varies depending on humidity levels that fluctuate throughout the day. Given the same high temperature in Pamban and Madurai, discomfort level may vary according to humidity. While India Meteorological Department (IMD) observations are made under protected conditions, those outdoors may feel higher temperatures, and denser population and traffic further add to the UHI effect, he says.

The combined effects of climate change, urbanisation, and natural climate variability have increased the likelihood of extreme heat events, underlining the need for effective heat plans and early warning systems, meteorologists say.

Intense summer heat events

According to the RMC, Tamil Nadu has witnessed a series of intense summer heat events over the past decade, with temperature records indicating a clear concentration of extreme heat in the north and interior districts. The decade’s most severe heat episodes occurred during May 2017 and May 2024. Data indicate that northern and interior Tamil Nadu continue to be the epicentre of extreme summer heat, with Vellore (which recorded the decade’s highest May temperature of 43.7 degrees Celsius) remaining a prominent hotspot over the last decade. With more districts experiencing high temperatures and warm nights, heat is emerging as one of the State’s significant weather-related hazards.

Though Tamil Nadu experienced temperatures lower than Telangana, coastal Andhra Pradesh, and north India, widespread 40-degree-mark temperatures and high humidity amplified heat stress, especially along the coast. Intense heatwave conditions across Telangana resulted in 48 heat-related fatalities. No mortalities were reported in Tamil Nadu, according to Mr. Durai.

Mahesh Palawat, vice-president (meteorology and climate change), Skymet Weather Services, said Banda in Uttar Pradesh emerged as one of the hottest places in the country this summer, recording temperatures of up to 48.3 degrees Celsius, and the temperature stayed above 47 degrees Celsius for several days. Interestingly, western Rajasthan, traditionally India’s hottest region during summer, did not witness extreme temperatures this year. Instead, severe heat was concentrated over southwest Uttar Pradesh, parts of Madhya Pradesh, Marathwada, and Vidarbha during May, he said.

IMD’s data indicate that average summer temperatures in Tamil Nadu’s hot weather districts have increased by about 0.5 degree Celsius to 0.9 degree Celsius in the past 35 years. Karur and Tiruchi show the strongest warming trends. Even a small increase in average temperature can substantially raise the frequency of hot days, warm nights, and heat-stress conditions in such hotspots, officials say.

Uncomfortable weather events

According to D. Sivananda Pai, Head, RMC, uncomfortable hot weather events have increased in recent years, driven by global warming. UHI effect contributed to discomfort, creating a difference of 4 to 5 degrees Celsius in real-feel temperatures between urban and nearby open areas. Land use and land cover changes are also triggers. Sea surface temperature anomalies across the tropical Pacific indicate a warming trend that may intensify from July. The Monsoon Mission Coupled Forecast System suggests further strengthening of El Nino conditions during the southwest monsoon, potentially reaching moderate to strong intensity. It may influence warm temperatures in Tamil Nadu in September. Its effect may extend till 2027, potentially leading to a warm winter next year. Normally, it is associated with good northeast monsoon. However, each year is unique, and there have been exceptions in the past, says Mr. Pai.

Mr. Palawat, too, notes that El Nino may not have any significant impact on Tamil Nadu and south peninsular region this year. Its high impact would reflect in rainfall patterns in central parts of India in August and September.

While much of the heat governance framework revolves around outdoor temperatures and daytime heat, a recent study in Chennai linking indoor temperatures and relative humidity by Climate Trends, a research-based consulting and capacity-building initiative, has found that residents face heat stress indoors, even after peak summer months. It documented persistent elevated nighttime temperatures. Indoor temperatures monitored across 50 households in Chennai between October 2025 and April 2026 were found to frequently exceed 32 degrees Celsius and the majority of them recorded at least four months of persistent heat exposure. Indoor temperatures peaked between 8 p.m. and 9 p.m., as concrete structures released the heat stored through the day, and night temperatures rarely fell below 31 degrees Celsius. The study also found that the structural characteristics of housing, including construction materials, played a decisive role in shaping indoor thermal conditions.

Heatwaves were notified as a State-specific disaster in Tamil Nadu in 2024, facilitating the use of State Disaster Response funds for preparedness and relief. The notification also provided for compensation for heat-related deaths and paved the way for a coordinated response involving health, disaster management, and local administration departments. Relief measures proposed included the provision of medical assistance and oral rehydration salts and access to drinking water in affected areas.

Meanwhile, the impact of rising temperatures is being felt across sectors. Outdoor workers, including construction and farm workers and street-vendors, are among the most exposed to heat stress. A 2026 study, ‘Quantifying the Impact of Heat Stress on Labour Productivity among Informal Outdoor Workers in Southern India’, led by researchers, including Vidhya Venugopal, and published in the journal Scientific Reports (Nature Portfolio), surveyed 1,560 outdoor workers in 11 districts of Tamil Nadu. It revealed that prolonged exposure to high temperatures can affect worker productivity and health, increase the risk of dehydration and heat-related illnesses, and place additional pressure on public health systems. “During summer, I start work early. But, within a couple of hours, the heat starts getting to me. I keep drinking water and take short breaks... By afternoon, I experience headache, fatigue, and dizziness,” says R. Vimala, a construction worker at Sriperumbudur.

State Heat Action Plan

As part of the efforts to strengthen preparedness, the State Heat Action Plan 2026 was launched by the Tamil Nadu State Disaster Management Authority and the Tamil Nadu Disaster Risk Reduction Agency. It focuses on localised risk assessment, instead of relying solely on State-level averages, by mapping localised heat vulnerability and developing a sector-specific threshold mechanism. It is aimed at improving early warning systems, taluk-level heat thresholds, and better coordination among government departments. Officials say daily district-level heat risk bulletins will be issued.

For workers, recommendations include rescheduling outdoor work and ensuring access to drinking water. In the health sector, the plan calls for enhanced surveillance of heat-related diseases and training of healthcare workers. The agency has also called for feedback through https://beta-tnsmart.rimes.int/index.php/Action_plan/HeatWave.

Retired bureaucrat K. Phanindra Reddy says that in the short term, awareness must be created about the dangers posed by heatwaves and the precautions to be taken, while the government takes measures to ensure drinking water supply to the vulnerable populations and prime the line departments to proactively respond to distress situations. Restoration of waterbodies and expansion of green cover must be long-term counter-measures.

The IMD plans to increase the use of heat indices and heat-stress monitoring rather than focus on temperature alone. Besides sharing annual climate report with the Tamil Nadu government, it plans to incorporate heat index during specific hours to measure thermal discomfort and realistic indication of ‘real feel’ temperature. However, activists point to a persistent gap between policy, planning, and execution. G. Sundarrajan of Poovulagin Nanbargal says, “There are enough scientific reports and action plans. But they remain only on paper.” He urges the government to address the UHI effect on a war footing by expanding urban green cover. One option is to transplant mature trees into cities. Their survival rate may initially be around 50%-60%, but it could improve with better management. While climate change is a global challenge, solutions must be tailored to local conditions.

(With inputs from Geetha Srimathi and Dennis S. Jesudasan)