Temperature gap across neighbourhoods in Mumbai highlights growing Urban Heat Island effect: Report

The India Meteorological Department (IMD) issued official heatwave warnings during the first half of the month, particularly between March 6 and 11, as temperatures soared close to 40 degree Celsius.

Mumbai: In what comes as a concern for Mumbai and the larger Mumbai Metropolitan Region (MMR), a new analysis has revealed alarming temperature variations across India’s financial capital, pointing to an intensifying Urban Heat Island (UHI) effect in the city.

MMR comprises the twin districts of Mumbai City and Mumbai Suburban and large parts of neighbouring areas of Palghar, Thane and Raigad.

The analysis by Respirer Living Sciences, a leading climate-tech startup dedicated to achieving cleaner air and accelerating the transition to cleaner energy, shows significant temperature variation between hotter Mumbai Suburbs and other cooler pockets across MMR in March 2025.

Between March 1 and March 22, 2025, suburban areas like Vasai West and Ghatkopar experienced average temperatures of 33.5°C and 33.3°C, respectively, while Powai—one of the city’s greener and less densely built areas—registered a much cooler average of 20.4°C.

This represents a striking 13.1°C difference within the same city.

UHI, a well-documented urban phenomenon, refers to the significant temperature difference between densely built urban zones and less developed or greener parts of a city. Heat-retaining infrastructure, such as concrete buildings and roads, a lack of vegetation, and localised pollution levels primarily drive this difference.

“Increasingly, we are witnessing micro-climate zones forming within cities like Mumbai,” said Ronak Sutaria, Founder and CEO of Respirer Living Sciences.

“These temperature differences are not just academic—they translate into higher heat stress and related health problems for residents, especially in poorly ventilated or overbuilt neighbourhoods,” he said.

According to data from 22 CPCB stations, Vasai West topped the list with an average temperature of 33.5°C, followed closely by Ghatkopar at 33.3°C, and Colaba (South Mumbai) at 32.4°C. In stark contrast, Powai, a relatively green and less built-up part of the city, recorded a much cooler average of 20.4°C. Other cooler areas included Chakala (Andheri East) at 23.4°C and Chembur at 25.5°C.

The temperature differences across the city showed that while 13.1°C gap was seen between Vasai West and Powai, Colaba registered 32.4°C compared to 23.4°C in Chakala, an urban heat difference of 9.0°C. Ghatkopar, at 33.3°C, was 7.8°C warmer than Chembur, which averaged 25.5°C.

“Microclimates are forming within Mumbai, and the data makes this undeniable. It’s not just about summer getting hotter—it’s about some neighborhoods facing disproportionate heat stress. That has implications for everything from public health and energy demand to urban planning and equity,” added Sutaria.

Interestingly, even Colaba, located on Mumbai’s southern tip and historically known for its coastal breezes, now appears on the warmer end of the spectrum—underscoring that even so-called “cool zones” are not immune to rising heat levels.

Sutaria stressed the need for zone-specific heat forecasting: “We cannot treat Mumbai as a single thermal unit. Our mitigation efforts—from tree plantation drives to heat action plans—must be customised based on hyperlocal data. Green infrastructure, reflective surfaces, and responsible architectural choices are all part of the solution to create healthy cities.”

The India Meteorological Department (IMD) issued official heatwave warnings during the first half of the month, particularly between March 6 and 11, as temperatures soared close to 40°C.

A combination of strong easterly winds and delayed sea breeze, caused by an anticyclone system, led to unusually high daytime temperatures, especially on March 9 and 10, when the mercury hovered around 37°C.

A fresh temperature spike followed from March 15 onward, with forecasts predicting a further 2–4°C increase and warnings issued for March 18.