Heat inequality in cities: what London and Delhi reveal about heat and daylight

A heatwave does not arrive in a city as a shared experience. Two residents can read the same forecast and still live through entirely different afternoons.

For one person, there may be a shaded balcony, an air conditioner that works, and employment that allows them to remain inside.

For another, the day might be spent outdoors at a construction site or running a street stall, followed by an evening in a flat with no fan and no electricity.

Casper Ebbensgaard and Kavita Ramakrishnan argue that urban planning too often overlooks that second reality.

Ebbensgaard is a lecturer in human geography at the University of East Anglia’s School of Environmental Sciences. Ramakrishnan is based in UEA’s School of Global Development.

Heat inequality in cities

In their view, heat and daylight are more than meteorology; they are also matters of fairness.

“Climate change is not experienced equally,” Ebbensgaard said. “Understanding how heat and daylight are felt in everyday life is essential for developing more inclusive and equitable cities.”

A single temperature figure for an entire city assumes residents experience heat in the same way. They do not.

Class, gender, and caste influence how a body copes with high temperatures, and one reading from a weather station cannot reflect that complexity.

People stuck outside during a heatwave

Delhi illustrates how far official measurements can diverge from lived conditions. In May and June 2024, the city recorded 121.8 degrees Fahrenheit (49.9 degrees Celsius).

A subsequent figure of 127.2 degrees Fahrenheit (52.9 degrees Celsius) was reported, although officials later attributed it to an instrument fault or to highly localised conditions at that particular location.

For outdoor workers, street vendors, and day labourers, there is often no shade to escape to.

Ebbensgaard and Ramakrishnan point to fatigue, dehydration, heatstroke, and death as the outcomes faced by people forced to remain outside during a heatwave of that intensity.

Power cuts made indoor heat worse

How hot a home becomes is not dictated by weather alone. Access to electricity matters as well, and when demand peaks, informal housing is often among the first to lose power.

During the May 2024 heatwave, outages across Delhi meant many residents were unable to run fans or other cooling devices.

As a result, indoor temperatures rose to dangerous levels, and people were deprived of proper sleep night after night.

The researchers describe Delhi’s challenge as too much sun with too few places to get away from it. In London, they argue, the problem can run in the opposite direction.

In London, new high-rise developments have reduced the daylight reaching neighbouring homes, and the researchers say that this loss carries health consequences.

Over time, inadequate natural light undermines sleep and emotional wellbeing.

According to the study, social housing tenants and other marginalised groups bear the brunt. Some residents told the researchers they can no longer see the sky from any window in their flat.

Daylight affects more than mood: it is the key signal the body uses to regulate its internal clock, which governs sleep, hormones, and energy levels across the day. When daylight is reduced, that system loses its strongest cue.

Residents pushed back on the numbers

Local authorities and developers frequently present new schemes in terms of floors delivered and homes added.

In London, residents’ groups and campaign organisations have argued that this way of describing development obscures what those figures mean for the people living alongside it.

“Recognizing daylight as a human right and linking it to mental health and disease resistance, as it has been in the UK, has strengthened advocacy,” Ebbensgaard said.

“By speaking about the impact that it would have, especially for vulnerable residents, the campaigners shifted the terms of the debate away from numbers alone to consider how daylight constitutes a fundamental part of creating healthy living environments for all residents, regardless of tenure.”

Ramakrishnan set out the wider purpose of placing London and Delhi side by side.

“The examples we present demonstrate how heat and daylight are encountered in the face of changing climate realities and top-down planning and housing development,” she said.

“As cities worldwide confront the growing impacts of climate change, this analysis provides new insights into the importance of placing human experience at the centre of urban planning and resilience strategies.”

What the data still misses

Official datasets may record water shortages, extreme heat, heavy rainfall, and pollution somewhere in municipal systems.

However, Ebbensgaard and Ramakrishnan say those records seldom show what such pressures do to health and day-to-day life, particularly in poorer neighbourhoods.

Housing condition, access to green space, work patterns, and the way an area is designed all influence who can adapt to a changing climate and who cannot. None of that is captured by a thermometer reading or a measure of sunlight.

The complete study appeared in the journal Urban Studies.