HOW HOT IS TOO HOT TO WORK?

Heatwave after heatwave after heatwave. As climate change brings more frequent and intense spells of extreme heat, and summer temperatures soar again in parts of the UK, many are wondering if the country should introduce a legal maximum workplace temperature; while employers already have a duty to protect staff from excessive heat, there is currently no law that specifies a point at which work should stop.

Offices without air conditioning, warehouses, factories, construction sites and commercial kitchens can all become uncomfortably hot during prolonged periods of warm weather, raising concerns not only about comfort but also about health and safety.

Under UK law, employers must ensure the health, safety and welfare of their employees “so far as is reasonably practicable”. The Health and Safety Executive (HSE) states that workplace temperatures should be “reasonable” and that employers should assess the risks posed by excessive heat. Measures such as improving ventilation, providing fans, supplying drinking water, relaxing dress codes and allowing more frequent rest breaks are all encouraged where appropriate. However, unlike the legal minimum workplace temperature of 16°C for most indoor work, there is no corresponding upper limit.

Supporters of a maximum working temperature argue that this leaves workers without clear legal protection. Trade unions have long campaigned for a maximum limit of 30°C for most workplaces and 27°C where work is physically demanding. They argue that heat stress can impair concentration, reduce productivity and increase the risk of accidents, particularly in jobs involving manual labour or machinery.

Those opposed to introducing a fixed maximum temperature argue that a single figure would be difficult to apply across the wide variety of workplaces found in the UK. A temperature that is manageable in an air-conditioned office may be unsafe in a warehouse, while a commercial bakery or foundry naturally operates at much higher temperatures. Humidity, ventilation, workload, clothing and the physical fitness of workers can all influence how people cope with heat, making temperature alone an imperfect measure of risk.

Several European countries have adopted a more structured approach. Germany, for example, expects employers to take action once workplace temperatures exceed 26°C, with increasingly stringent measures recommended at 30°C. At 35°C, a workplace is generally considered unsuitable unless additional protective measures are in place.

Belgium uses a different system altogether, measuring heat stress through the Wet Bulb Globe Temperature index, which takes into account humidity, radiant heat and air movement as well as air temperature. Thresholds vary according to the physical demands of the job, recognising that workers carrying out strenuous tasks are at greater risk.

Spain has strengthened protections for outdoor workers following successive heatwaves, requiring employers to adapt or suspend work where official extreme heat warnings are issued and workers cannot be adequately protected. Parts of Italy have also introduced temporary restrictions on outdoor work during periods of extreme heat, particularly in sectors such as construction and agriculture.

These approaches reflect a growing recognition that extreme heat is becoming an occupational health issue rather than simply an inconvenience. As average temperatures rise, many countries are adapting employment law alongside wider climate resilience measures.

The UK may ultimately face a similar decision. While existing health and safety legislation provides employers with flexibility to respond to individual circumstances, critics argue that the absence of a clear legal benchmark creates uncertainty for both employers and employees. Others maintain that strengthening guidance and improving enforcement may prove more effective than introducing a single statutory temperature limit.

With scientists warning that heatwaves are likely to become more common in the years ahead, the question is no longer whether workplaces need to adapt to hotter conditions, but whether current laws are sufficient to protect workers. Whether that results in a legal maximum temperature or a more sophisticated heat-risk framework remains to be seen, but the issue is unlikely to disappear as the UK’s climate continues to change.