Britain's record-breaking June heatwave cost the economy £1.15 billion in lost output and erased 24 million working hours in a single week, according to a study published on 22 July by the Grantham Research Institute on Climate Change and the Environment at the London School of Economics (LSE) and the Euro-Mediterranean Center on Climate Change (CMCC). The heatwave, which ran from 18 June to 1 July, produced England's warmest June since records began in 1884, with a provisional national high of 37.7°C recorded at Lingwood, Strumpshaw Hill in Norfolk on 26 June.
The researchers surveyed 1,950 adults across the UK about the week beginning 22 June, when temperatures in London reached 36°C. Participants were asked how the heat affected their working hours, their ability to sleep, and their commuting arrangements. On average, respondents reported working 0.47 fewer hours that week. A further 3.6% said they did not work at all during that period, equivalent to roughly 1.25 million workers nationwide and an estimated £0.38 billion of the total economic loss, according to the study.
The lowest paid bear the greatest burden
The heat did not land equally across the workforce. Workers in construction, agriculture, and other physically demanding outdoor roles cut their hours by significantly more than those in sedentary or air-conditioned environments. As Shouro Dasgupta, environmental economist at the CMCC and visiting senior fellow at the Grantham Research Institute, noted: the study found that beyond the aggregate £1 billion figure, the greatest effects fall on outdoor and physically demanding workers, many of whom are already among the lowest paid in the labour force.
“"While £1 billion is lost overall, the greatest effects are borne by outdoor workers and those in physically demanding jobs, many of whom are among the lowest paid in the labour force. Extreme heat is widening existing inequalities in the labour force." — Shouro Dasgupta, CMCC and LSE Grantham Research Institute”
Health impacts were widespread. Some 87% of survey respondents reported at least one health-related effect during the heatwave week, ranging from disrupted sleep and fatigue to more serious symptoms including dizziness, fainting, and heart palpitations. Women, workers under 35, and those with existing health conditions were the most likely to report harm, according to the study. The researchers note that their £1.15 billion figure is likely a conservative estimate, as it captures only lost hours rather than reduced effort per hour worked.
A regulatory gap under mounting pressure
The findings land amid a deepening political debate about workplace heat rules. Britain has no legally mandated maximum working temperature. Under the Workplace (Health, Safety and Welfare) Regulations 1992, employers are required only to maintain a "reasonable" indoor temperature, a standard unions argue is unenforceable during extreme heat. The Trades Union Congress and Unison have long called for a legal ceiling of 30°C for indoor work, and 27°C for strenuous physical labour. A parliamentary petition for a binding 25°C maximum gathered over 6,000 signatures this month alone.
In May 2026, the government's independent Climate Change Committee recommended that ministers commit to a national maximum workplace temperature. The government has since confirmed that the Health and Safety Executive (HSE) will consult later this year on updating its Approved Code of Practice, though no new legal threshold has been set. A Maximum Workplace Temperature Bill is also progressing through the House of Commons in the current parliamentary session.
“"Our findings point to a country that remains insufficiently adapted to the changing climate. The government cannot continue to ignore extreme heat." — Elizabeth Robinson, director, LSE Grantham Research Institute”
A separate assessment by Verdant, a London-based economic policy think tank, places the total cost of the June heatwave to the UK economy at least £2.4 billion, a figure that incorporates infrastructure failures and equipment damage on top of the productivity losses the LSE study measured. Looking further ahead, Verdant estimates that if no action is taken, cumulative output losses from heatwaves could reach at least £25 billion by the end of 2030. June's heatwave was the second of three to strike western Europe within three months this year, a pattern that researchers say will become more frequent as global CO2 concentrations continue to rise.
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