Working in Extreme Heat

Working in Extreme Heat

TUC advice

TUC’s Eight steps to keep cool and interactive guide, Too hot, too cold. 


TUC Cool it Guide:

HSE advice

HSE advice is that although there is no law for maximum working temperature, or when it is too hot to work, employers must keep workplaces at a comfortable temperature.  

HSE has practical guidance: on what you can do to manage the risks so people can work safety in hot conditions. 

RMT advice 

The impact of climate change means that we are increasingly seeing very high temperatures in the summer months.

To address this RMT safety reps should ensure that their employer plans for summer temperatures before they become a problem, meaning that employers have a working in hot weather policy and that, in consultation with their RMT safety reps, they risk assess the risks of temperature or heat and have control measures in place to remove or reduce these risks.


In offices or similar environments, the temperature in workplaces must be reasonable. But there is currently no law for maximum working temperature, or when it is too hot to work, although employers still have a legal duty to provide a “reasonable” temperature. The Workplace (Health,Safety andWelfare) Regulations 1992, regulation 7, states that “during working hours, the temperature in all workplaces inside buildings shall be reasonable.” How this regulation is applied depends on the nature of the workplace.

Under the Health and Safety at Work Act 1974 employers have a general duty to ensure the health, safety and welfare of their employees and under the Management of Health, Safety, and Welfare Regulations the employers duty is to assess and control risks from work.

Along with the TUC, RMT has for many years campaigned for maximum workplace temperatures, demanding a change in the law so that employers must attempt to reduce temperatures if they get above 24°C and workers feel uncomfortable.

These are not impossible demands; such guidance exists around the world. For example, in the United States regulations say working temperatures should not go beyond 24° C; Spanish guidelines state that working temperatures must not go beyond 27°C indoors or 25°C for physical activity; in Germany, 26°C is generally considered the maximum for indoor work; in China, when temperatures reach 37°C, outdoor work is banned during the hottest three hours of the day, and at 40°C it must stop altogether.

Not having such protections in the UK puts workers at risk:

Heat stress

This is when the body’s means of controlling its internal temperature starts to fail. As well as air temperature, factors such as work rate, humidity and clothing worn while working may lead to heat stress.

Heat Exhaustion

This is when a person becomes very hot and starts to lose water and salt from their body, leading to symptoms of feeling sick, faint and sweating heavily - signs of which are dehydration, muscle cramps, rashes, sunburn, fainting and loss of concentration leading to accidents.

It will take at least 30 minutes to cool the body once it has overheated; there will be no long-term complications if the person is taken to a cool place to recover, given water to drink and unnecessary, heavy clothing is removed.

Heat stroke

In the most extreme cases of heat exhaustion, heat stroke can occur – the symptoms of which include convulsions and loss of consciousness which can lead to death. Because of this, heat stroke requires immediate medical treatment.

Skin Cancer

Outdoor workers are three times more likely to develop skin cancer. The HSE says that 4,500 people are diagnosed with skin cancer every year because of outdoor working. Prolonged exposure to the sun can also lead to skin ageing more rapidly. In the long-term, eyesight problems are also associated with radiation exposure and glare.

Some workers may be particularly vulnerable to the effects of extreme heat:

–  Pregnant women

During pregnancy, the body must work harder to cool down both the woman’s body and that of her unborn baby.This means a pregnant woman is more likely to get heat exhaustion or heat stroke compared with other workers. Pregnant women are also more likely to become dehydrated.–  

- Menopausal women

For women experiencing the menopause hot weather is one of the main triggers for hot flushes – more intense ones too.

- Workers over 65

- Obese workers

- Disabled workers

- Those on certain medication

Indoor work

As the temperature goes up people sweat without moving, stress levels rise, concentration levels fall, mistakes increase, productivity goes down and accident levels rise.

If workers are doing manual work, there is a greater loss of fluids leading to dehydration and potential heat stress as the core body temperature rises. All these problems become worse if the humidity is also high, as the body is unable to cool itself through sweating as the air is already loaded with moisture.

The Workplace (Health, Safety and Welfare) Regulations 1992 state that thermometers should be available at convenient distances from every part of the workplace to enable temperatures to be measured.

Risk assessment control methods could include:

  • Using fans or other mechanisms to cool the air, as well as adequate ventilation (if temporary cooling units are used these should be replaced on a permanent basis to avoid annual disagreements over their supply)
  • Windows being shaded to deflect direct heat and glare which is a relatively cheap method to use
  • Moving workspaces away from windows and other heat sources
  • Using blinds to block out the sun
  • Relaxing dress codes and uniform policies
  • The provision of free cold drinks
  • The ability to take extra breaks, preferably in cooler areas
  • Adjusting shifts to avoid travelling in peak heat.

Outdoor work 

There is an increased risk from sunstroke, sunburn and heat exhaustion particularly when work is physically strenuous. Heat stress is more likely to occur if the air is humid/still or there is direct heat radiation, and the exposure is for long periods.

Employers must work with safety reps to introduce measures to protect their staff who work outdoors when temperatures rise, including:

  • Considering halting work altogether under extreme conditions
  • Considering rescheduling work at cooler times of the day
  • Educating workers about the early signs of heat stress
  • Changing work practices, so less outside work needs to be done during the hottest months and at the time of day when the sun is at its highest
  • Allowing staff to take plenty of breaks and providing a supply of preferably cool drinking water, to avoid dehydration by replacing water lost following sweating 
  • Providing canopies or coverings over open areas and shaded areas for breaks
  • Providing lightweight, close woven fabric protective clothing with long sleeves
  • Providing lightweight hats, which are brimmed. If hard hats are provided, that these have neck protection.

Workers should be involved in the selection of PPE. Some tasks may necessitate the wearing of vapour impermeable PPE, but, if not, this should be avoided, as clothing must be such that heat can escape.

Providing such clothing is more effective than providing sunscreen, which is also difficult to apply in dusty and dirty conditions and harder to monitor its correct usage. Also, sunscreen may lure workers into a false sense of security. However, sunscreen will still be needed for the face - and for hands if gloves are not worn.

Employers should provide sunscreen and advice on the need for protection. Sunscreen of at least 20spf (sun protection factor), although preferably at least 30, with both UVA and UBV (ultraviolet) protection, to be applied an hour before exposure and re-applied every 2 hours. A “more is better” approach is recommended to the application of the sunscreen. Sunscreen creates a barrier between the worker and the risk, and as such should be considered personal protective equipment.


The heat can be dangerous for workers whose jobs involve driving, as any driver suffering from fatigue is a risk to themselves and other people. Vehicles used for long journeys should be temporarily taken out of use if they cannot sustain a reasonable temperature, for example if they do not have air conditioning.

Ability to stop work on health and safety grounds agreement

Safety reps should seek to agree with their organisations a procedure whereby the worker can stop work on health and safety grounds, as follows:

  • Create a safety check list that the worker can fill out prior to the start of a job/process
  • Include an element around environmental conditions incorporating heat
  • The document to contain a stop work element that employee can sign off
  • Ensure supervisor is informed, resolution is discussed.
  • Task/job is halted if agreed hot weather will cause detrimental effects to health
  • Conditions are reviewed by management and union reps.

If such a procedure cannot be agreed, please refer to advice below around stopping work on health and safety grounds and contact your Regional Organiser for advice.

For advice on Stopping work on Health and Safety grounds see RMT “Serious and Imminent Danger “guidance,