Working in Extreme Heat:

What the Law Says and What Employers Must Do

With the UK now under a red weather warning for extreme heat, many of our members are facing temperatures that make safe working genuinely challenging. Whether you’re outdoors, in a vehicle, in a cab, or inside a building that traps heat, it’s important to know your rights, your employer’s legal duties, and what the Health and Safety Executive (HSE) actually expects during periods of dangerous heat.

This isn’t just about comfort. It’s about safety, health, and the law.

There’s No Legal Maximum Temperature — But That Doesn’t Mean Employers Can Ignore the Heat

A common myth is that because the UK has no legal maximum working temperature, employers can simply carry on as normal. That’s not true.

While the law doesn’t set a specific upper limit, it does require employers to take action when temperatures become unsafe.

Under the Health and Safety at Work etc. Act 1974, employers have a duty to:

• Protect the health, safety, and welfare of employees

• Assess risks and take reasonably practicable steps to control them

• Provide a safe working environment

And under the Management of Health and Safety at Work Regulations 1999, employers must:

• Carry out suitable and sufficient risk assessments

• Put in place measures to remove or reduce risks

Extreme heat is a foreseeable risk, especially during a red weather warning, and employers cannot simply ignore it.

What HSE Actually Says About Working in High Temperatures

HSE is clear: employers must manage the risks of working in hot conditions, whether indoors or outdoors.

Key expectations include:

1. Carry out a heat‑specific risk assessment

This should consider:

• Air temperature

• Humidity

• Radiant heat (sun, machinery, vehicles)

• Workload and physical exertion

• PPE that traps heat

• Individual factors (health conditions, pregnancy, medication)

A generic risk assessment is not enough during extreme weather.

2. Take action to reduce the risk

HSE lists several “reasonably practicable” measures, including:

• Providing cool drinking water

• Increasing breaks

• Rotating tasks to reduce physical strain

• Adjusting start/finish times to avoid peak heat

• Providing shade or temporary shelters

• Improving ventilation

• Relaxing dress codes or PPE where safe to do so

• Allowing workers to stop if they feel unwell

If the employer can take a measure and it’s reasonable, they must.

3. Monitor workers for signs of heat stress

Heat stress is a serious medical risk. Symptoms include:

• Dizziness

• Headache

• Confusion

• Excessive sweating or, dangerously, no sweating

• Nausea

• Rapid heartbeat

HSE is clear: if a worker shows signs of heat stress, the work must stop immediately.

4. Consult with workers and safety reps

Employers must involve safety reps in assessing risks and agreeing controls. This is not optional, it’s a legal requirement under the Safety Representatives and Safety Committees Regulations 1977.

Outdoor Work: Additional Legal Duties

For outdoor workers, including telecoms engineers, delivery staff, postal workers, and field technicians, employers must also consider:

• UV exposure

• Heat from direct sunlight

• Long periods of physical exertion

• Lone working risks

  
  

HSE expects employers to provide:

• Sun protection advice

• Access to shade

• More frequent rest breaks

• Water and hydration planning

• Adjusted workloads

  
  

During a red weather warning, these controls become essential, not optional.

Indoor Work: Heat Can Be Just as Dangerous

HSE highlights that indoor environments can become hazardous due to:

• Poor ventilation

• Heat from machinery

• Enclosed spaces

• Vehicle cabs

• Server rooms or equipment bays

  
  

Employers must ensure:

• Ventilation is adequate

• Fans or cooling systems are provided where possible

• Work is paused if temperatures become unsafe

  
  

What Workers Should Do

If you feel unwell, dizzy, faint, or unable to continue safely, stop work immediately and report it. Heat stress can escalate quickly and is a medical emergency.

You should also:

• Report unsafe temperatures to your manager and safety rep

• Request a heat‑specific risk assessment

• Ask what control measures are being put in place

• Document any refusal to act

Your union is here to support you — and we will challenge employers who fail to meet their legal duties.

What the Union Expects from Employers Right Now

Given the current red weather warning, we expect employers to:

• Conduct urgent heat‑specific risk assessments

• Implement additional breaks and hydration plans

• Provide shade or cooling where possible

• Adjust working hours to avoid peak heat

• Allow workers to stop if conditions become unsafe

• Consult with safety reps on all measures

  
  

Anything less is a breach of their legal responsibilities.

If You Have Concerns — Contact Us

If your workplace is not taking heat risks seriously, or if you feel unsafe, please get in touch with your branch. We can advise, support, and intervene where necessary.

Extreme heat is not “just part of the job.” It’s a serious health and safety risk, and the law is clear: Employers must protect workers.