Can trees cool cities? On a heatwave afternoon, you already know the answer — if you know where to stand.

The heat you can feel, street by street

Step out in Mumbai on a peak summer afternoon, and the heat doesn’t feel uniform.

In dense, built-up neighbourhoods, temperatures can hover around 43°C. A short drive away, where tree-lined roads and parks break up the concrete, it can drop to nearly 32°C. Move further towards greener edges near the city’s outskirts, and it can fall to 25–26°C.

Same city. Same hour. A gap of more than 10°C.

This isn’t anecdotal. A 2023 data-driven analysis by Sustainable Energy for All (SEforALL) highlights how temperatures within Mumbai vary sharply depending on green cover and built density.

As heatwaves tighten their grip across Indian cities — from Delhi to Bengaluru — this gap is becoming more than a matter of discomfort. It is a growing public health concern.

What we feel on our skin is not just climate change. It is also the design of our cities.

What makes a city hotter?

Cities are built to trap heat.

Concrete, asphalt, and glass absorb solar radiation during the day and release it slowly after sunset. Roads and buildings act like storage units, keeping nights warmer and days harsher.

Trees, soil, and water behave very differently.

They reflect more sunlight, retain moisture, and cool the air through shade and evapotranspiration — the process by which plants release water vapour.

When this natural layer is reduced, cities begin to heat unevenly. This is known as the urban heat island........

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