Study on the Impact of Extreme Heat at the Tamilaga Vettri Kazhagam Conference!

Poovulagin Nanbargal’s demand to predict weather based on UTCI!

Tamizhaga Vettri Kazhagam (TVK) recently organised its second state conference in Madurai, Tamil Nadu on August 21, 2025. According to news reports, hundreds of people fainted in the harsh heat, and two men tragically lost their lives. In the event footage, thousands of participants could be seen in a state of fatigue. This incident warrants serious attention and cannot be sidelined as a random occurrence.

This was a dire re-enactment of TVK’s first mega-conference held on October 27th, 2024 at Vikravandi, Tamil Nadu, where many people had fainted, and mass fatigue was prevalent across demographics. Similarly, on October 6th, 2024, in the Chennai Air Show, countless people fainted, and at least five people died. Heat related complications in mass gathering have therefore become a recurrent crisis in Tamil Nadu.

During the 2024 Lok Sabha elections, thirty-four government officials who were involved in election duty succumbed to death in Uttar Pradesh. On June 16, 2024, thousands of people who were on their way to the Hajj pilgrimage died within a few hours due to extreme heat. The reason behind these casualties was extreme heat stress, which is a side-effect of rising global temperatures.

The Intergovernmental Panel on Climate Change (IPCC) reports that the average temperature in Southeast Asia is increasing rapidly due to global warming. This has been the reason behind the rising frequency of heatwaves in India. Based on the IMD definition, if a place experiences 4.5 – 6.4 °C higher than the historical average temperature for 48 hours, it can be classified to be a heat wave. Yet, no heatwave warnings were given during the two TVK conferences, the Chennai Air Show, or even during the 2024 Lok Sabha elections, although multiple deaths were reported. Hence, there is an urgent need to reanalyse these events, and the conceptualisation of heat warnings itself.

Extreme heat stress for even a few hours could be fatal. The Lancet Journal’s 2024 Countdown report states that several places in Asia are already experiencing uncompensable heat stress, and this is likely to increase in the coming years. What this translates to is that several states in India, including Tamil Nadu, are already facing extreme temperatures that can potentially cause heat-related mortality.

The human body must maintain an average temperature between 36.4–37.2°C, a balanced condition that is termed as ‘homeostasis’. Any significant increase or decrease in body temperature can lead to fainting, heat stroke or even death. Through millions of years of evolution, mankind gained the ability to adapt its body to the changing external temperature. Organs such as the skin, brain, and nervous system play a crucial role in maintaining the homeostasis of our body. When external temperature increases, blood flow rises to release excess heat through the skin. If this does not cool enough, sweat glands produce sweat to cool the body. However, this mechanism functions only within certain limits.

Increasing temperatures and humidity as a result of global warming have maimed this cooling process. The human body cannot withstand extreme heat stress beyond a certain exposure time. At higher humidity levels, the cooling effect of sweat is also severely hampered, which could lead to increased core body temperatures. If left unchecked, the internal body temperature can rise uncontrollably, causing severe illnesses like heat stroke and even death.

This phenomenon is the reason behind countless deaths across the world due to heat stress. Most notably, the 2003 European heatwave which killed 70,000 people is a tragic reminder. In response to this event, the European Union introduced the ‘Universal Thermal Climate Index’ (UTCI), an ‘equivalent temperature’ (°C) that accurately reflects thermal stress. It considers factors such as air temperature, relative humidity, wind speed, and the mean radiant temperature to measure the human body’s response to outdoor thermal environments. UTCI can be used to not only identify potentially fatal heat conditions but also to understand the varying effects of heat stress on the human body at various UTCI levels.

At present, the IMD relies solely on maximum temperature for warnings. It uses 48 hours as the standard duration of extreme temperatures in order to announce heat waves. However, it does not measure extreme heat stress on specific days or during particular hours. IMD also does not consider the humidity or land surface temperature (LST) or while issuing precautionary warnings. This means that no public warning system exists in response to extreme heat stress. Considering the successes of the UTCI system in the European Union, IMD must also adopt bioclimatic models such as the UTCI model, especially when issuing precautionary warnings. This approach is particularly crucial in a state like Tamil Nadu, where the urban population is high. The growing density of urban buildings, shrinking green cover, and vanishing water bodies etc. intensifies the effect of urban heat islands. These combined effect of these anthropogenic factors have created deadly extreme heat conditions which threaten countless human lives. The incidents mentioned above are proof of the seriousness of this deadly heat.

Poovulagin Nanbargal has been continuously monitoring these events. As part of this, the UTCI values during TVK’s Madurai conference were analysed, revealing dangerously high UTCI values (> 38°C) from 10:30 a.m. to 6:30 p.m.[1]. The research found that between 12:30 and 4:30 p.m., the UTCI values exceeded 43°C. In such conditions, a person can potentially faint within one hour. Around 3:30 p.m., the temperature peaked at 45°C, a level at which extreme heat could cause fainting or even heat stroke within half an hour. It is such extreme heat that resulted in two innocent lives being lost, and hundreds of people fainted due to these conditions. Those affected by heat stress would have experienced fatigue, dizziness, and nausea for several hours to days. Women, children, and elderly people would have suffered the most from the thermal dose with high likeliness of sustained heat illnesses.

We verified our on-location calculations with the ERA5 HEAT dataset for thermal comfort indices (UTCI), released by the ECMRWF Copernicus platform. Our findings had a very high degree of correlation with their 27.5 km resolution values [2]. Considering that the ERA5 dataset underestimates UTCI values and approximates microclimatic effects, we believe that our calculations are more accurate in this regard.

Our research findings raise serious questions about the safety of our public spaces, especially the ones involving social gatherings. Considering this dire state of things, Poovulagin Nanbargal puts forth the following requests:

The central and state governments should announce extreme heat as a natural disaster.
The IMD and other research centres should conduct studies on the methodologies to measure extreme heat.
The IMD should take measures to give early warnings and announcements on extreme heat.
The UTCI method, which is designed to predict extreme temperatures, should be adopted by IMD.
Adequate laws, research should be undertaken to regulate large crowds from a thermal environment perspective.
Vulnerable groups most affected by extreme heat should be identified, and specific policies should be made by the central and state governments to protect them.

Reference image 1: Calculated UTCI