When Is It Too Hot to Work?

• There is no legal maximum temperature for workplaces in the UK; however, employers must protect workers from the risks associated with extreme temperatures.
• Working in high temperatures can lead to serious health and safety risks.
• Employers must assess the risks of extreme temperatures in both indoor and outdoor work environments.
• Employers must take all reasonable measures to control the risks of extreme temperatures, including training staff on relevant risks and control measures.

There’s no legal maximum workplace temperature. However, the Health and Safety at Work etc. Act 1974 places an overarching duty on employers to ensure workers’ health and safety.

Adding to this duty, the Management of Health and Safety at Work Regulations 1999 require employers to assess work-related risks and implement adequate control measures. This includes the health and safety risks of extreme temperatures in both indoor and outdoor work environments.

Other pieces of legislation explicitly mention workplace temperature requirements. Under the Workplace (Health, Safety and Welfare) Regulations, employers must provide a ‘reasonable’ temperature in all workplaces inside buildings. The same requirement for construction sites is found in the Construction (Design and Management) Regulations 2015.

What is considered a ‘reasonable’ temperature depends on the work environment and the type of work being carried out.

The Health and Safety Executive’s Approved Code of Practice (ACOP) for Workplace (Health, Safety and Welfare) Regulations 1992 states that a minimum workplace temperature should be:

• 16°C for most workplaces
• 13°C if work is physically demanding

While the ACOP does not give a figure for the maximum temperature for workplaces, the Trades Union Congress (TUC) has called for an upper limit of 30°C, or 27°C for rigorous physical work.

The TUC recommend this upper limit because extreme heat is a clear health hazard. Working in high temperatures poses risks to the health and safety of workers, which can be particularly severe for those with pre-existing health conditions or pregnant women.

If heat poses a risk to workers, employers must determine if it is too hot to work safely and what can be done to bring temperatures down to a reasonable level.

Working in high temperatures is a physical and psychological risk.

The normal human body temperature is generally around 36.5°C to 37.5°C. If this temperature rises and the body can’t cool down, heat stress occurs.

Excessive heat stress can lead to heat-related illnesses, such as heat exhaustion, characterised by symptoms including heavy sweating, weakness, cold and clammy skin, nausea and dizziness.

If left untreated, heat exhaustion can progress to heat stroke, a medical emergency characterised by a body temperature exceeding 40°C. Heat stroke can involve red skin, headache, confusion, loss of consciousness and seizures. Without immediate intervention, it can cause irreparable organ damage and can be fatal.

Heat exposure can lead to slower thinking, difficulty concentrating and memory lapses, all of which increase the risk of mistakes and accidents. Prolonged heat can also cause dehydration, which further worsens concentration and coordination.

When temperatures rise to uncomfortable or unsafe levels, employers must take proactive steps to ensure that working conditions remain reasonable. Here is what employers should do:

Employers must identify when heat becomes a workplace hazard and assess the risk it poses to workers. This assessment involves:

• Monitoring indoor and outdoor temperatures
• Identifying areas or roles at particular risk (e.g. kitchens, warehouses, outdoor tasks)
• Factoring in the physical intensity of tasks and required protective clothing
• Considering vulnerable individuals, such as:
  • Pregnant employees, older workers and those with chronic conditions.
  • Workers on medication that affects hydration or thermoregulation (the ability of the body to maintain its core temperature)
  • Outdoor workers who are exposed to direct sunlight

To help manage temperatures, employers should:

• Provide fans, air conditioning or air cooling systems where reasonably practicable
• Increase ventilation by opening windows and using ventilators or extractor fans
• Use shading or reflective blinds to block direct sunlight
• For outdoor workers, provide covered rest areas and portable shelters

Flexible scheduling can help reduce heat exposure:

• Adjust working hours to cooler parts of the day (e.g., early starts or evening shifts)
• Introduce more frequent breaks, ideally in cool, covered areas
• Alternate between more and less strenuous tasks throughout the day

In hot weather, employers should relax strict dress policies where possible:

• Allow lightweight, loose-fitting and breathable clothing
• Where safe to do so, modify personal protective equipment or swap to lighter alternatives

Staying hydrated helps the body regulate its temperature. Employers should:

• Ensure unlimited access to cool drinking water near workstations
• Encourage workers to drink small amounts regularly, rather than waiting until thirsty
• Consider providing electrolyte drinks in extreme heat

Effective communication with employees helps manage heat risk more proactively:

• Discuss heat risks during team meetings, toolbox talks or safety briefings
• Encourage workers to voice discomfort or suggest improvements
• Work with employee representatives or safety committees to develop and refine policies for working in extreme temperatures

Employees should understand the risks of working in the heat and how to respond:

• Provide training on the signs of heat stress, including how to recognise and report symptoms
• Ensure staff know when to take a break and when to seek help
• Display posters or quick-reference guides in staff rooms or on-site

Training should be one of your control measures. If workers understand the risks of extreme heat and the early signs of heat stress, they’ll be better equipped to stay safe on scorching days.

Our online Heat and Cold Stress Training highlights the risk factors and control measures for working in extreme temperatures. It explains what workers can do to stay safe when temperatures soar, and what to do if someone is affected by heat stress.

By the end of the course, users will know how to recognise the signs of heat and cold stress and better protect themselves and others from the risks of extreme temperatures.