Extreme heat in the workplace is no longer simply a question of comfort. With temperatures forecast to approach 37°C in parts of the UK, employers are being urged to treat heat as a foreseeable workplace hazard that can affect health, concentration, safety and productivity.
The latest hot spell places the issue firmly back on the workplace agenda. The Met Office has issued an amber extreme heat warning, with very hot conditions expected across parts of the country.
For millions of UK workers, however, the working day cannot simply be moved into the shade.
Construction workers, delivery drivers, warehouse staff, factory operatives, agricultural workers, engineers, care workers and people required to wear heavy protective equipment may all face increased risks when temperatures rise.
The central question is therefore not whether a workplace has crossed a single number on a thermometer. It is whether the work can still be completed safely.
Is there a maximum legal workplace temperature in the UK?
There is currently no fixed maximum workplace temperature at which employees automatically have a legal right to stop working.
However, this does not remove an employer’s responsibilities. Government guidance confirms that temperatures in indoor workplaces must be “reasonable”, while employers must comply with wider health and safety law.
The Health and Safety Executive has made the position clear: heat is a workplace hazard and should be managed in the same way as other risks.
That means employers should assess who may be exposed, examine the nature of the work and introduce proportionate controls before somebody becomes unwell.
Why temperature alone does not reveal the full danger
A thermometer reading does not tell the whole story.
Heat stress can be affected by humidity, physical effort, direct sunlight, air movement, machinery, protective clothing and the length of time a person remains exposed.
A worker performing heavy manual duties in protective equipment may face a much greater risk than somebody sitting in a ventilated office at the same temperature. New workers and those who have not had time to become accustomed to hotter conditions may also be more susceptible.
Other workers may be particularly vulnerable because of pregnancy, medication, age or an existing condition affecting the heart, lungs or the body’s ability to regulate temperature.
According to the HSE’s heat-stress guidance, employers should speak to workers about early symptoms and consider specialist occupational health advice where necessary.
Warning signs workers should not ignore
Heat-related illness can develop gradually, but it can also become serious quickly. Warning signs may include:
- Headache, dizziness or unusual tiredness
- Heavy sweating or hot, dry skin
- Nausea, cramps or weakness
- Difficulty concentrating or poor coordination
- Confusion, fainting or loss of consciousness
Workers experiencing symptoms should stop, move to a cooler place and report the problem immediately. Confusion, collapse or suspected heatstroke requires urgent medical assistance.
Heat can also create secondary safety risks. Reduced concentration, sweaty hands, fatigue and slower reactions can increase the likelihood of mistakes involving vehicles, machinery, tools, ladders or hazardous substances.
What employers should do during extreme heat
The correct response will depend on the workplace, but practical measures are already available.
Indoor measures may include improving ventilation, using blinds to reduce solar heating, moving workstations away from direct sunlight and deploying suitable cooling systems.
Workloads and performance targets may also need temporary adjustment. A production target designed for an ordinary day may not be safe or realistic during extreme heat.
Where protective equipment is essential, it should not simply be removed while hazardous work continues. Employers should instead review exposure periods, arrange cooler recovery breaks and consider whether suitable alternative equipment is available.
These actions are not workplace luxuries. They are sensible controls designed to keep people safe and operations functioning.
Protecting workers can also protect productivity
There is a strong economic case for acting early.
Experimental modelling from the Office for National Statistics estimated that hot days produced average annual productivity losses of £1.2 billion in Great Britain between 1998 and 2021, even when adaptation measures were assumed.
The ONS cautions that these are modelled estimates rather than recorded losses. Nevertheless, the findings underline a basic point: asking people to continue at an unchanged pace in unsafe heat may reduce output rather than preserve it.
Mistakes, absence, equipment disruption and heat-related illness can be far more costly than additional breaks, altered hours or temporary cooling measures.
What workers can do if the workplace becomes dangerously hot
Workers should report concerns as soon as possible and explain the practical effect of the conditions. Useful details may include the temperature, humidity, lack of airflow, physical demands, protective clothing and any symptoms experienced by colleagues.
Where possible, concerns should be recorded in writing. Workers can ask whether the heat risk assessment has been reviewed and what temporary controls are being introduced.
The Workers Union believes that no UK worker should feel pressured to ignore signs of illness simply to maintain a normal pace during exceptional conditions. Reporting dizziness, confusion or heat exhaustion is a safety action, not a failure of commitment.
As hotter and longer heatwaves become more frequent, employers will need plans that can be activated before conditions become dangerous. A portable fan introduced after somebody collapses is not a heat-management strategy.
The workplaces best prepared for extreme heat will be those that listen to workers, review risks early and recognise that protecting health is essential to keeping Britain working.
