Mumbai weather updates: Experts call for urgent action amid heatwaves, say tailored plan is necessary

Mumbaikars cover up to protect themselves against the scorching heat. Pic/Sayyed Sameer Abedi

As Mumbai sweats through increasingly brutal summers, public health experts are sounding the alarm over the city's inadequate preparation for rising heatwaves. While residents - from delivery persons, and construction workers to postmen, traffic cops and senior citizens in slums - struggle to stay cool, experts say Mumbai still lacks a city-specific, data-driven Heat Action Plan (HAP) to combat the threat of extreme heat.

Dr Dileep Mavalankar, the former director of the Indian Institute of Public Health, Gandhinagar, and the architect of India's first HAP in Ahmedabad, emphasised that Mumbai must urgently formulate a comprehensive, long-term strategy tailored to its unique coastal geography and dense urban population.

"There is an urgent need for cities like Mumbai to develop HAPs that are based on local climate, demography, and health data," said Dr Mavalankar. "This includes appointing a dedicated nodal officer to coordinate implementation, creating public awareness campaigns, and issuing regular heat alerts not just on red alert days, but also during orange and yellow alert days."

He pointed to Ahmedabad's model, where 15 years of temperature and mortality data were used to establish thresholds for issuing warnings - 40°C for yellow, 43°C for orange, and 45°C and above for red. These thresholds are now tied to real-time alerts shared with the India Meteorological Department (IMD).

"Most cities, including Mumbai, are yet to systematically collect and correlate hospital admissions or mortality data with temperature. Without that, we're flying blind when it comes to understanding the real health burden of heatwaves," he warned.

In the absence of this data, Mumbai's current heat response has been largely reactive and fragmented. Public messaging is minimal, cooling infrastructure is nonexistent, and many vulnerable communities remain unaware or unprotected during heat spells.

City needs ‘Heat Index'

Dr Mavalankar highlighted that Mumbai's climate demands a different strategy from landlocked cities like Ahmedabad. "Humidity plays a major role here. The temperature might not look alarming on paper, but the discomfort and danger are real," he said.

He recommended that Mumbai develop its own heat stress index, combining temperature and humidity to better reflect lived conditions. Institutions like the Indian Institute of Technology (IIT) Bombay could collaborate with local agencies to build this model, similar to what IIT Delhi has done for the rest of the country.

Emergency readiness

While Ahmedabad has introduced emergency cooling measures like cold baths in hospitals and ice-packed ambulances, such provisions are missing in Mumbai. "Hospitals here need to be trained and equipped to recognise and treat heat-related illnesses quickly," Dr Mavalankar added.

He also called for "cooling zones" across the city: shaded rest spots, cool bus stops, hydration points, and heat shelters at public spaces and transit hubs. These would provide much-needed relief for those working outdoors or travelling long distances during peak heat hours.

Rethinking infra/work hours

Dr Mavalankar stressed that cities must not only respond to immediate emergencies, but also rethink their long-term infrastructure. "Urban greening, heat-resistant building materials, and sustainable design must be central to future development," he said.

He further recommended staggering work hours for outdoor workers including traffic police, sanitation staff, and dabbawalas to help them avoid peak heat exposure. "During extreme heatwaves or unusually hot days, the local administrations should permit early shifts, such as 8 am to 11 am, and mandate rest breaks during the hottest parts of the day to reduce health risks," Dr Mavalankar said.

‘Time to act'

The BMC and other civic bodies have yet to announce a standalone HAP, even as Mumbai experiences longer and more frequent spells of extreme heat. Experts believe now is the time to act. "Heat preparedness is not just about emergency response, it's about designing cities that can survive and thrive in a warming world," Dr Mavalankar said. "Mumbai must move fast. Climate change will not wait."

Lubaina Rangwala, associate director, World Resources Institute (WRI) India, said, "In coastal cities, temperatures higher than 35°C are dangerous because they surpass the body's ability to cool off after exposure and result in severe illnesses, and fatalities. In this scenario, across the country, it is a national emergency that cities and districts implement the HAPs that are well monitored and tailored to the needs of those most vulnerable."

A 2021 study by researchers from Jamia Millia Islamia, Osmania University, and Aligarh Muslim University, revealed that Mumbai lost 81 per cent of its open land, 40 per cent of its green cover, and nearly 30 per cent of its water bodies between 1991 and 2018. During the same period, built-up areas doubled, contributing to a 2°C rise in average temperature and intensifying the Urban Heat Island (UHI) effect.

The study, published in the Journal of the Indian Society of Remote Sensing, linked this shift to rapid, unplanned urbanisation and the replacement of natural surfaces with concrete. Professor Atiqur Rahman, a co-author, noted that materials like concrete trap heat, creating microclimates that worsen city temperatures.

Researchers called for urgent urban greening, better land-use planning, and adherence to World Health Organization (WHO) and European Union guidelines for minimum per capita green space. They also recommended rooftop and vertical gardening, and community tree planting, and discouraged glass-heavy facades to reduce heat stress and restore environmental balance in the city. "Rather than rushing to draft a separate HAP for the city, it's high time Mumbai focused on implementing what we already know needs to be done," added Rangwala.

"Any HAP requires three key elements - hazard analysis, exposure analysis, and vulnerability assessment. Much of this groundwork was already laid out under the Mumbai Climate Action Plan (MCAP) in 2022. The broad-level actions have been recommended and the urgent need now is implementation. This means institutional shifts and departmental-level changes. We already understand the hazard; the focus should be on acting, not repeating the process with yet another plan. We need a target-oriented approach," she said.

10 hottest places

Between April 10 and April 14, the districts of Nandurbar, Akola, and Chandrapur in Maharashtra consistently ranked among the top ten hottest locations in India, highlighting the intense heatwave sweeping through the region. On April 10, Nandurbar recorded a scorching 46.5°C, making it the hottest location in the country that day. Akola also featured prominently at the sixth position with 43.5°C. On April 11, Akola retained its high rank at number two with 42.8°C. Nandurbar did not appear in the top ten that day.

On April 12, the focus shifted to Chandrapur, which topped the chart with 42.6°C, while Khandwa, bordering Maharashtra, rounded off the list with 41.5°C. Nandurbar and Akola were absent from the top ten, but their temperatures remained high locally.

On April 13, Nandurbar once again surged to second place with 43.2°C, just behind Barmer. Akola ranked fifth at 42.4°C, while Chandrapur was seventh with 42.2°C, showcasing how multiple districts from Maharashtra dominated the heat charts. Finally, on April 14, Nandurbar was ranked fourth with 43.5°C, Akola secured the fifth spot with 43.0°C, and Chandrapur dropped out of the top ten by a small margin.

Data: IMD and Vagaries of the Weather

Voices

Dr Dileep Mavalankar
Former director, Indian Institute of Public Health, Gandhinagar

‘There is an urgent need for cities like Mumbai to develop HAPs that are based on local climate, demography, and health data. This includes appointing a dedicated nodal officer to coordinate implementation, creating public awareness campaigns, and issuing regular heat alerts'

Lubaina Rangwala
Associate director, World Resources Institute India

‘Any HAP requires three key elements - hazard analysis, exposure analysis, and vulnerability assessment. Much of this groundwork was already laid out under the Mumbai Climate Action Plan (MCAP) in 2022. Broad-level actions have been recommended. The urgent need now is implementation'