The recent surge in temperatures across North India has caused serious concern, with cities facing intense and prolonged heat. Maximum temperatures have exceeded normal levels by 4-8°C across Haryana-Delhi, Punjab, Uttar Pradesh, Madhya Pradesh, Bihar, Jharkhand, Rajasthan, Odisha, and West Bengal. Rising humidity and warmer nights have significantly worsened heat stress, especially in warm-humid and moderate climate zones. So even when the temperature is relatively lower, it feels much hotter.
A heatwave is declared when the departure from normal temperature is between 4.5°C and 6.4°C, and a severe heat wave is declared when the departure exceeds 6.4°C. However, the entire region is currently experiencing heatwaves based on actual maximum temperatures above 45°C. When such extreme heat conditions persist for an extended period, they can pose risks to public health and infrastructure. Historically, heat waves in India lasted for five to 15 days. This year, it has persisted through most of May and June.
Cyclone Remal, which originated in the Bay of Bengal, disrupted the arrival of monsoons from this region, exacerbating the intensity of heat waves. The monsoon stream through the Arabian Sea has also progressed steadily, sparing South India from similar heat wave conditions. This changing pattern underscores a direct link between monsoon variability and the duration of heat waves.
Cities are particularly vulnerable due to the urban heat island effect, exacerbated by greenhouse gas emissions. Factors such as increased congestion, paved surfaces, depletion of water bodies, loss of vegetation, and high-density settlements trap heat and contribute to higher urban temperatures. Additionally, cities are no longer cooling at night at the same rate as a decade ago. Heat waves are interconnected with other hazards, such as forest fires, electrical faults, droughts, water scarcity, and lightning.
The socioeconomic impacts of heat waves in India are pronounced. Workers in sectors such as construction, hawking, and vending are disproportionately affected. Women working in kitchens and residents in tin-roofed homes also face extreme discomfort. Reliance on air conditioning is not a sustainable solution.
Large gatherings, such as pilgrimages and elections, magnify the heat wave’s impact. The proximity of people in crowds creates a microclimate where body heat accumulates, leading to hyperthermic syndrome, a form of heatstroke. This is further exacerbated by high humidity that hinders the body’s ability to cool itself through sweat evaporation. The recent general elections saw polling officials lose their lives due to heatstroke in several states, including West Bengal, Odisha, Bihar, and Uttar Pradesh. In 2023, when 14 people died during a political rally at Kharghar in Navi Mumbai, humidity played a significant role. These incidents highlight the severe risk to public safety during such events, emphasising the need for better preparedness and immediate measures to mitigate heat-related hazards.
Longer and more intense heat waves result in a higher relative risk of mortality, falling into two categories: Direct heat stroke deaths and increased cardiovascular disease (CVD) incidence. Each 10°F increase in mean daily temperature can lead to a 2.6 per cent rise in CVD mortality. However, accurately measuring heat wave-related deaths presents challenges. The government’s health-related illness surveillance has significantly improved preparedness, keeping annual heat stroke deaths below 100. Despite this, the increasing burden of diseases poses a significant public health challenge. Prioritising public health interventions based on the intensity and duration of heat waves and recognising their broader implications in the context of climate change is essential.
The National Disaster Management Authority (NDMA) has initiated heat action plans (HAPs) — with the first HAP for Ahmedabad. NDMA is encouraging the preparation of local HAPs to address specific needs at the district, city, and town levels. Appointing dedicated heat officers could enhance the coordination and implementation of these plans. These HAPs require the participation of local governments, civic groups, and communities, promoting behavioural change, adaptation, and urban planning. There are three key strands of support that HAPs must offer.
One, it is crucial to improve temperature monitoring across cities and towns through a dense network of weather stations. This network should provide granular data on microclimates, enabling the identification of high-risk areas.
Two, preparedness measures are essential to mitigate the immediate effects of extreme heat. Regulating working and school hours can help protect vulnerable populations. Ensuring adequate water availability through public drinking water facilities and awareness campaigns is vital. Enhancing health system preparedness by training healthcare workers to recognise and treat heat-related illnesses will improve community resilience.
Three, implementing solutions such as improving and restoring water bodies, increasing vegetation cover, and promoting cool roofs and better ventilation in buildings will enhance thermal comfort.
In the next few years, cities will require significant knowledge support to prepare and monitor heat action plans. Further, financial support for HAPs needs to be evolved based on a pooling arrangement, with governments at different levels and the private sector contributing to the cause. While heat waves are currently considered local disasters, their increasing severity will necessitate a broader national approach.
The rising temperatures forecasted by climate models are becoming a reality, demanding a comprehensive and coordinated response. We must marshal all available resources, wisdom, and commitment to develop effective adaptation and mitigation strategies to protect our communities and ecosystems from the escalating threat of heatwaves.
The writer is member, National Disaster Management Authority. Views are personal
