A hot day does not hurt everyone equally. A banker in an air-conditioned office and a delivery rider waiting at a traffic signal may live in the same city, but they face very different summers.
That is the uncomfortable point behind a new global heat-risk mapping exercise. It comes as US forecasters expect El Nino, the natural climate pattern that can raise temperatures and disrupt weather, to emerge between May and July this year.
The timing matters. May was already 0.5°C warmer than the 1991-2020 global average. The Northern Hemisphere is now moving deeper into its hottest months. For India, the Gulf and wider Middle East, this is not an abstract climate headline. It is a daily health, work and infrastructure issue.
Researchers at the University of Oxford looked at cities with more than one million people. They did not simply ask which places get the hottest. They studied three things together: the heat people face, how vulnerable residents are, and how well a city can help them cope.
That broader method produces a sharper warning list. Among the 10 cities most exposed to severe heat risk are Basra in Iraq, Ahmedabad and Nagpur in India, Faisalabad and Hyderabad in Pakistan, Bamako in Mali, Lagos and Kano in Nigeria, Conakry in Guinea, and Barranquilla in Colombia.
Together, these cities have more than 37 million people at risk.
For Indian readers, Ahmedabad and Nagpur stand out immediately. Both cities know heat. Ahmedabad has already built public systems around heat warnings after deadly past summers. Nagpur, in central India, often sits inside the country’s furnace zone during peak summer.
But the study’s lesson is wider than any one city. A heat crisis becomes dangerous when weather, poverty, age, housing, electricity costs and weak urban greenery collide.
The first measure is heat exposure. This includes land surface temperature, air temperature, humidity, wind speed and the heat radiating from nearby surfaces such as walls, floors and windows.
That last detail is important. Anyone who has walked beside a concrete wall in May knows the body does not experience temperature as a neat number on a weather app. Pavements, glass, metal roofs and apartment blocks throw heat back at people.
Humidity also changes the risk. A city may not show the world’s highest temperature reading, but if the air feels heavy and sweat cannot cool the body properly, the danger rises.
This is why humid tropical cities can rank high on exposure even when the thermometer does not look extreme. Hot and dry cities also dominate this measure, especially those close to the equator or in arid regions.
Jeddah is a useful Gulf example. The Saudi city ranks high for heat exposure. Yet it does not sit at the very top of the overall risk list because other factors reduce the final score.
That is where the second measure comes in: vulnerability. This looks at how likely people are to suffer once heat arrives. The researchers used factors such as income levels, the share of young children and older adults, and access to air conditioning.
This measure heavily affects sub-Saharan African cities. Places with lower income, younger populations and limited cooling access face a double burden. People may be physically exposed and financially unable to protect themselves.
Kano in Nigeria ranks especially high on vulnerability. Jeddah, by contrast, falls sharply in this part of the ranking because its broader economic and cooling conditions look different.
For India, this distinction is familiar. Heat does not only punish by geography. It punishes by job type, housing quality and income. A family in a dense settlement with poor ventilation faces a different risk from a household that can afford cooling, steady electricity and shaded mobility.
The third measure is coping capacity. This is where city design and affordability enter the picture. Researchers looked at infrastructure, tree cover, vegetation and electricity prices as a way to understand whether cooling is practical.
This matters deeply across arid South and West Asia. Sparse greenery means less shade and less natural cooling. High power costs can make fans and air conditioners too expensive, even when machines are available.
In simple terms, vulnerability asks who is exposed. Coping capacity asks what shields exist when the heat arrives.
Basra shows how risks can pile up. The Iraqi city scores very high across all three areas: heat exposure, vulnerability and limited coping capacity. It is one of the few cities that appears near the top for both exposure and vulnerability while also facing a coping deficit.
That combination gives Basra the highest composite risk in the study.
For the Gulf, Basra is more than a distant Iraqi data point. It sits in a region where summer heat shapes labour hours, power demand, transport, water use and public health. When temperatures climb, the pressure does not stop at hospitals. It reaches construction sites, ports, delivery networks, schools and electricity grids.
Dubai and the UAE have stronger infrastructure than many at-risk cities. Cooling is widespread, building standards are higher, and emergency messaging reaches residents quickly. Still, the study’s caveat deserves attention: a low citywide risk score does not mean nobody gets hurt.
In any modern city, low-income workers, outdoor staff and people in informal or poorly cooled housing can face severe heat stress. The average can hide the person standing outside at noon.
For businesses, this is a productivity issue as much as a health issue. Heat slows outdoor work. It raises cooling bills. It strains logistics. It can affect travel comfort, tourism timing and event planning. In cities built around mobility, retail and services, extreme heat has economic teeth.
For families, the practical advice remains plain but serious. Heat alerts deserve attention. Children, elderly people and those with medical conditions need earlier precautions. Outdoor exercise, errands and work should move away from peak heat where possible. Hydration is not a lifestyle tip in this context. It is basic protection.
For city governments, the study points towards targeted action. Tree cover, shaded streets, affordable electricity, cooling shelters, early warnings and worker protections can reduce harm. Air conditioning helps, but it cannot be the only answer. It costs money, uses power and often misses the people who need protection most.
The most useful part of this research is its refusal to treat heat as just weather. A city becomes dangerous when heat meets inequality and weak infrastructure. That is why some very hot cities fare better than expected, while others become urgent warning signs.
El Nino may come and go. Summer will return every year. The cities that prepare now will not only save lives during heatwaves. They will protect workers, keep services moving and make daily life less punishing for the people who keep urban economies alive.
