Heat is no longer a future climate risk. It is already here.
Across continents, high temperatures are being pushed higher by forces acting at once: human-caused warming, very warm oceans, dry soils, slow-moving high-pressure weather systems and El Niño conditions that have now developed in the tropical Pacific.
El Niño is a natural warming of part of the tropical Pacific that can shift weather patterns around the world. It is not the cause of climate change, but when it develops in a climate already warmed by greenhouse gas pollution, it can add another push to global temperatures and regional extremes.
The science is clear. Greenhouse gases have raised the baseline, so heatwaves now begin from a warmer starting point. Record ocean heat adds more energy to the climate system. Dry ground can intensify heat, because less of the sun’s energy goes into evaporating water from soil and plants, and more goes into heating the air.
Weather patterns decide where that heat lands. A “heat dome” happens when a high-pressure system settles over a region. Air sinks, clouds are suppressed and temperatures can climb for days. The danger grows when nights remain hot, because bodies, buildings and infrastructure get little chance to cool.
El Niño’s effects vary by region and season, so it will not explain every heatwave in 2026. But it is now being added to long-term warming, and that combination can raise the risk of more extreme heat, drought or heavy rainfall in some regions, including parts of Asia, Australia and the Americas.
In the UK, Kew Gardens reached 35.1°C in late May, provisionally breaking the national May temperature record for the second day in a row. The previous record, before the 2026 heat, was 32.8°C, reached in 1922 and 1944.
Elsewhere, the same pattern is visible. Spring 2026 was the hottest spring recorded in France since records began in 1900. In the United States, March 2026 was the warmest March on record for the contiguous US (the lower 48 states). India’s meteorological service issued an extended heatwave outlook into early July for parts of northern, central and eastern India, while China’s National Climate Center has forecast above-normal summer temperatures, especially in southern China and Xinjiang in the north west. In Australia, Tasmania, Victoria and New South Wales have just had one of their ten warmest autumns on record.
Heat kills
Heat often kills without leaving obvious damage behind: it pushes bodies past what they can tolerate.
High temperatures can cause dehydration, strain the heart, worsen kidney disease and aggravate respiratory illness. Heat can also affect mental health and increase distress. Older people, babies, people with chronic illness, outdoor workers and those living alone are among those at higher risk.
Hot nights make heatwaves more dangerous because the body has less chance to recover. Research has linked high nighttime temperatures with increased heat-related deaths. In an overheated bedroom, care home or hospital ward, strain can continue for hours.
The death toll from heat is large, but often underestimated because heat may worsen existing illness rather than appear as the sole cause of death. A 2025 European analysis estimated 62,775 heat-related deaths in Europe in 2024 alone. The Lancet Countdown reports that heat-related deaths among older people have risen sharply, and that hundreds of thousands of people now die globally each year from heat.
Heat also puts pressure on the systems people rely on. Hospitals fill faster. Care homes become harder to cool. Rail lines buckle. Roads soften. Rivers warm and water quality declines. Electricity demand rises as people use fans and air-conditioning, while low river flows can affect water quality and supply. A power cut can disrupt cooling, transport, water systems, shops, hospitals and communications.
What helps during a heatwave
People can reduce risk, especially if they act before they feel ill.
Cool the body early: drink water regularly, use shade, take cool showers and put wet cloths on the skin. People who have been told to restrict fluids because of heart failure, kidney disease or another medical condition should follow medical advice about how much to drink.
Avoid being outside in the hottest part of the day where possible. Outdoor workers, athletes and people who travel on foot need particular protection.
Keep homes cooler before they overheat. Close curtains or blinds during the day, especially on windows facing the sun. Open windows after sunset if it is cooler outside than inside. Sleep in the coolest room available.
Check on people at higher risk. Do they have water, shade, medication, a way to get help and somewhere cooler to go if home becomes unsafe?
Take official warnings seriously. Follow heat-health alerts, local weather warnings and public health advice. Have a simple plan for medicines, transport, pets, food, drinking water and somewhere cooler to go if needed.
Seek urgent medical help if someone becomes confused, faints, has a seizure, collapses, has very hot skin, has a very high temperature, or does not improve after being moved somewhere cooler and cooled down.
Inequality and infrastructure
Personal precautions save lives, but they cannot make unsafe housing safe, cool a badly ventilated care home or protect outdoor workers without changes to working conditions.
Heat risk is shaped by inequality. People without trees, insulation, ventilation, secure work, clean water or affordable energy are less able to avoid exposure, cool their homes or recover after extreme heat. The same pattern applies between countries: communities that have contributed least to climate change are often disproportionately affected, because they have fewer resources for adaptation, healthcare, infrastructure and disaster response.
Adapting to heat has to be collective: cooler housing, shaded streets, heat-resilient hospitals, reliable water systems, worker protections, public cooling spaces and early warning systems that reach the people who need them.
Heat and drought are increasingly linked emergencies. Heat increases demand for water and electricity. Drought can reduce supply. Together, they can create failures across health, transport, food, water and energy. Water, health, energy and climate planning need to be connected, because stress in one system can quickly spread to another.
The next heatwave will be reported as weather. It should also be understood as a test of housing, healthcare, infrastructure and public protection. A hotter world is already here. The question now is how many heat-related deaths and system failures governments are prepared to accept as normal.
