Too hot to work – when can I leave work because of the heat?

The UK is currently in the midst of a heatwave, with the Met Office issuing its first Red Extreme heat warning for 18 and 19 July. With temperatures potentially rising to 40°C in the southeast of the UK, the heat may have population-wide adverse health effects. In some countries, workers are asked to work from home or not work at all when temperatures exceed certain thresholds. But what is the situation in the UK?

Workplace temperatures

Under the Workplace (Health, Safety and Welfare) Regulations 1992 employers need to ensure that temperatures in the workplace are reasonable. However, besides ensuring and maintaining suitable workplace temperatures, employers must also ensure that the air is clean and fresh.

That being said, there are no legal minimum or maximum working temperatures. This means that there is no set temperature at which it is too cold or too hot to work.

The Health and Safety Executive (HSE) recommends a minimum temperature of 16ºC (and 13ºC for anyone doing rigorous physical work). However, no maximum temperature limit exists. 

This means that in the UK there is no temperature at which it is considered too hot to work and, consequentially, no temperature at which staff can leave work because of heat.

How can employers determine if staff are struggling?

Even though no maximum temperature limit exists, employers must take care the workplace does not become unreasonably hot.

As part of their workplace risk assessments, carried out to determine whether a workplace is safe to work in, employers need to consider:

  • air temperature – this is the temperature surrounding the body
  • radiant temperature – the heat that radiates from a warm object (eg machinery, molten metal and even the sun)
  • air velocity – the speed of air moving across the workers. This may help cool them if the air is cooler than the environment and help move stagnant air
  • humidityhigh humidity (80%+ humidity) prevents staff from sweating as much and, therefore, prevents heat reduction. This is especially important where staff wear non-breathable vapour-impermeable personal protective equipment (PPE)
  • what clothing staff wear – wearing too much clothing or PPE can cause heat stress (even if the environment isn’t too hot). Wearing clothing that isn’t warm enough can result in cold injuries (eg frostbite or hypothermia)
  • the average rate at which staff work – the more physical the work is, the hotter workers get and the more heat needs to be lost to ensure they don’t overhear. In addition, employers should also consider a worker’s age, sex, fitness level, size and weight as these all contribute to how heat-sensitive someone is

For more information on these factors, see the HSE’s guidance on The six basic factors.

Thermal comfort checklist

To help employers determine whether staff are experiencing thermal discomfort, the HSE has created a thermal comfort checklist

Workers may be at risk of thermal discomfort if they select ‘yes’ for at least two of the options on the checklist. Employers should then carry out a detailed workplace risk assessment to determine whether the circumstances are suitable for work, bearing in mind the specific environment worked in. For example:

  • workers working outside – employers are responsible for introducing rest breaks, providing drinking water and encouraging workers to hydrate regularly
  • workers who typically wear warmer business clothes – employers may consider adopting a more casual dress code to help them handle heat better

What steps can employers take?

Even before undertaking a new risk assessment or asking staff to complete a thermal comfort checklist, employers should always listen to their staff’s concerts. Anyone who is suffering thermal discomfort in the workplace should speak to their manager and/or the HR department. If staff are struggling, employers should consider what steps they can take to make the situation bearable. 

Examples of measures employers can put in place to help cool down the workplace include:

  • providing air conditioning or fans
  • allow workers to adjust thermostat settings or open windows
  • instal blinds on windows
  • move workstations away from sunny or overly hot areas 
  • insulate any exposed pipes that become hot
  • rotate workers and workstations if some staff members have to handle uncomfortable temperatures for extended periods
  • ensuring staff are not wearing more PPE than necessary
  • encouraging staff to drink water frequently and providing easy access to cold water (eg in the form of a water cooler)

For more information, see the HSE’s guidance on Controlling thermal comfort.


For more information on workplace health and safety, read our guide on Health and safety. If you have any questions or concerns, do not hesitate to Ask a lawyer.

Rebecca Neumann