Extreme heat is claiming hundreds of thousands of lives yearly and draining trillions from global economies through lost labour, crop failures, infrastructure strain and soaring energy demand, with Europe and developing nations bearing the heaviest burdens.

Extreme heat, once viewed mainly as a seasonal discomfort, has become the deadliest climate risk, responsible for roughly 489,000 deaths annually – more than floods, storms, earthquakes and wildfires combined. The 2025 Lancet Countdown on Health and Climate Change reports that heat-related mortality averaged 546,000 deaths per year between 2012 and 2021, a 63 per cent rise since the 1990s. In 2024, the hottest year on record, the average person faced about 16 extra dangerous heat days attributable to climate change; infants and people over 65 endured more than 20.

This summer’s early and intense heatwaves in Europe, the world’s fastest-warming continent, have already exacted a heavy price. Various media reports note nearly 20,000 excess deaths across the region. Germany recorded more than 9,800 heat-related deaths, disproportionately among those aged 75 and older. France attributed about 5,700 deaths to its June heatwave alone, while the UK estimated 2,877 fatalities across four separate heat episodes. In the United States, more than 40 million people faced extreme heat warnings in July, with at least 25 confirmed deaths in the first half of the year – the second-hottest such period on record. South Korea logged 2,025 heat-related health cases and 19 deaths since mid-May; Japan saw 18,600 hospitalisations and 45 deaths in one late-July week as temperatures hit 40°C in places. Even animals suffered: three lions died of heatstroke at Tokyo’s Tama Zoo.

Wildfires, supercharged by hotter, drier conditions, compound the human toll. Climate change has at least doubled the risk of the extreme weather driving recent destructive fires in France and multiplied it twentyfold in Spain, according to World Weather Attribution analysis. EU countries have already lost more than 460,000 hectares to fire this year, with Spain and France hardest hit. Canada alone burned an estimated 6 million hectares – its third-largest wildfire season. Globally, the share of tree cover loss caused by fires rose from 27 per cent in 2001–2022 to 43 per cent in 2023–2025.

Productivity and Agriculture Take the Brunt

The economic damage is equally stark and accelerating. Heat exposure wiped out a record 639 –640 billion potential work hours worldwide in 2024 – 98 per cent higher than the 1990–99 average – equivalent to roughly $1.09 trillion in lost income, or nearly 1 per cent of global GDP. Agriculture accounted for about 63.5 per cent of those lost hours (rising to 75.5 per cent in low-HDI countries), followed by construction. Low- and medium-HDI nations suffered the heaviest relative burden.

In Europe, June’s heatwave alone is estimated to have cost the continent’s grain harvest about €2 billion. France revised its cereal output downward by 4.1 million tonnes (≈€891 million), Hungary by 2.4 million tonnes (≈€444 million). The Energy and Climate Intelligence Unit warned these shortfalls could increase import dependence and push up global commodity prices later in the year. A separate analysis put the UK’s June heatwave economic loss at $1.5 billion through reduced working hours, poorer sleep and health impacts. July became England’s driest on record, triggering drought declarations across half the country and hosepipe bans.

Allianz research shows productivity collapses above a roughly 30°C threshold: each additional degree in the 30–35°C range cuts output per hour by about $1.3 (constant PPP), or roughly 3 per cent. Energy demand for cooling rises about 1.2 per cent per degree. Under a stress scenario replaying the five hottest recent years in ascending order through 2030, cumulative GDP losses could reach 5–7 per cent in the most exposed economies – $240 billion for France, $354 billion for Japan, $147 billion for Italy, $131 billion for Germany and $120 billion for Spain. Investment would fall even harder (around 8 per cent on average), creating a self-reinforcing drag on future capacity. Fiscal balances are projected to deteriorate by about 0.5 per cent of GDP annually as tax revenues shrink and healthcare, emergency repairs and inflation-indexed transfers rise.

Cities already lose 4–8 per cent of GDP to extreme heat in studied locations, with impacts projected to multiply three- to fivefold by 2050 without stronger action. Women in the informal sector worldwide forfeit an estimated $57 billion in earnings each year – 4–11 per cent of their wages – because of limited protections and higher exposure.

Infrastructure, Energy and Cascading Risks

Critical infrastructure is buckling. France temporarily halted three nuclear reactors over cooling-water and environmental concerns. The Rhine, a vital European trade artery, has hit record-low levels, with further drops expected. Roads, railways and power grids face heat-related damage and demand spikes; electricity prices in parts of Europe have already set records during heatwaves. Drought and heat together have driven food inflation higher by an estimated 0.4–0.9 percentage points in the short term.

Looking ahead, the International Labour Organisation projects that heat stress will reduce global working hours by 2.2 per cent by 2030 – equivalent to 80 million full-time jobs – costing $2.4 trillion in GDP. By 2035, annual productivity losses could reach $2.4 trillion and fixed-asset losses for listed companies $445 billion. Christian Aid’s Counting the Cost 2025 report found the ten costliest climate disasters of the past year alone inflicted more than $122 billion in (mostly insured) damage, with the true total far higher once uninsured and human costs are included.

Uneven Vulnerability and the Path Forward

The burden falls disproportionately on the poorest, the oldest, outdoor workers, informal-sector women and tropical regions least responsible for emissions. Rural areas often lose a higher share of output than cities. Europe’s ageing population, dense urban fabric designed to retain heat, and relatively low air-conditioning penetration (about 19 per cent versus 90 per cent in the US) heighten exposure. Developing countries face steeper relative GDP hits and have fewer resources for adaptation.

Yet the science is clear: most of these deaths and losses are preventable. Expanding early-warning systems, heat-health action plans, workplace protections (rest schedules, shade, hydration), green and blue urban infrastructure, building standards that prioritise cooling, and rapid emissions cuts can sharply reduce the toll. The Lancet Countdown stresses that climate action remains “a lifeline,” capable of saving millions of lives while protecting economies. Without accelerated mitigation and adaptation, today’s record heat will become tomorrow’s baseline – and the human and economic bill will only grow heavier.