Managing Temperature in the Workplace

With another heatwave forecast for the UK, The HSE discusses how to keep employees safe during hot weather.

Is It Too Hot To Work?

There’s no law for maximum working temperature, or when it’s too hot to work, because every workplace is different.

No meaningful upper limit can be imposed because in many indoor workplaces high temperatures are not seasonal but created by work activity, for example in bakeries or foundries.

However, employers must stick to health and safety at work law, including:

  • keeping the temperature at a comfortable level
  • providing clean and fresh air

Outdoor Working

When working outdoors, the weather can have a serious impact on worker’s health if the risks have not been properly managed.

This impact may be immediate or occur over a longer time, leading to conditions like skin cancer.

The weather can also affect a worker’s ability to keep safe, for example when handling machinery.

There are simple actions you can take to protect people working outdoors.

In Hot Environments

  • Reschedule work to cooler times of the day
  • Provide more frequent rest breaks and introduce shading to rest areas
  • Provide free access to cool drinking water
  • Introduce shading in areas where people are working
  • Encourage workers to remove personal protective equipment when resting to help encourage heat loss
  • Make sure workers can recognise the early symptoms of heat stress

Working in the Sun

Too much sunlight can cause skin damage including sunburn, blistering and skin ageing. In the long term, it can lead to an increased risk of skin cancer.

You can find more guidance on outdoor workers and sun exposure.


When working in very hot conditions, dehydration can seriously affect a worker’s health and their ability to function safely.

How To Reduce The Effects of Dehydration

  • Encourage workers 
  • to frequently drink cool water (rather than tea, coffee or carbonated drinks)
  • It is better to drink in small amounts to compensate for the effects of sweating
  • Do not rely on workers saying they are thirsty. It is not a good indicator of dehydration, more an early sign that they are starting to suffer from its effects
  • When working at a high rate in heat stress conditions, workers should drink around 250 ml (half a pint) every 15 minutes
  • If you have workers exposed to heat stress conditions, encourage them to be adequately hydrated before they come to work

Where Ability to Drink is Restricted

Some situations make it harder for workers to drink, for example if they are wearing personal protective equipment (PPE).

In these situations you could encourage workers to drink:

  • 500 ml (a pint) of water per hour before work starts
  • the same amount during their rest periods

If water loss is significantly greater through increased sweating, then they should increase the amount they drink proportionately.

Even if workers replenish lost sweat with equal amounts of water, they may still be dehydrated due to lost salt from the body. It is therefore a good idea to have drinks that contain the salts needed.

What is Heat Stress?

Heat stress happens when the body’s way of controlling its internal temperature starts to fail. As well as air temperature, factors such as work rate, humidity and work clothing may lead to heat stress.

You and your workers must be aware of how to work safely in high temperatures. This means identifying the factors that can cause heat stress, and how to avoid it.


A Typical Heat Stress Situation

Someone wearing protective clothing and doing heavy work in hot and humid conditions could be at risk because:

  • sweating is restricted by clothing and humidity
  • body heat increases due to work rate and, so core body temperature rises
  • the body reacts by producing more sweat, which may cause dehydration
  • heart rate also increases, putting more strain on the body

How do I Assess the Risks?

Where there is a possibility of heat stress occurring, you must assess the risks to workers. You need to consider:

  • work rate – the harder someone works the more body heat generated
  • working climate – this includes air temperature, humidity, air movement and working near a heat source
  • work clothing and personal protective equipment (PPE) – these may prevent sweating and other ways of regulating temperature
  • a worker’s age, body type and medical factors (eg a hormonal imbalance) may affect their tolerance of heat

Firstly, talk to your workers (and their safety representatives) to see if they are suffering early signs of heat stress. If there is a problem, you may need expert advice from occupational health professionals.

We have a heat stress checklist (PDFto help you control the risks.

How Can I Reduce the Risks?

Remove or reduce the sources of heat where possible.

Limit Work Rate and Length of Exposure

Provide mechanical aids where possible to reduce the work rate.

Regulate the length of exposure to hot environments by:

    • only allowing workers to enter the workplace when the temperature is below a set level or at cooler times of the day
    • issuing permits to work that specify how long people should work in situations where there is a risk
    • providing periodic rest breaks and rest facilities in cooler conditions

Read more about temperature in the work place at