Working in Above-Average Temperatures: Keeping Employees Safe in Hot Weather

Periods of unusually warm weather can create significant health and safety challenges for businesses. Whether employees are working outdoors, in offices, warehouses, workshops or other indoor environments, higher temperatures can affect comfort, concentration, productivity and, in more severe circumstances, health.

With warmer periods becoming an increasingly important consideration for employers, businesses should understand their responsibilities and have practical arrangements in place for managing heat at work.

Is There a Maximum Legal Working Temperature?

A common question during hot weather is: “How hot does it have to be before employees can stop working?”

There is no specific legal maximum workplace temperature and no single temperature at which work must automatically stop. The Health and Safety Executive (HSE) explains that workplaces and working activities vary too greatly for one maximum temperature to be appropriate. This does not mean employers can ignore high temperatures.

Under the Workplace (Health, Safety and Welfare) Regulations 1992, the temperature inside workplaces must be reasonable during working hours. Regulation 7 also requires excessive effects of sunlight on indoor workplace temperatures to be avoided.

The Management of Health and Safety at Work Regulations 1999 also require employers to assess risks to workers and introduce suitable controls. The HSE specifically identifies workplace temperature as a risk that should be considered for both indoor and outdoor work.

Therefore, the important question is not simply “What does the thermometer say?” but:

“Is the temperature creating a risk to the health, safety or welfare of our employees and are we doing enough to control that risk?”

Temperature Alone Does Not Tell the Whole Story

Two employees working at the same air temperature may experience very different levels of heat exposure. The HSE identifies six important factors when considering thermal comfort:

• Air temperature.
• Radiant temperature, including heat from the sun or machinery.
• Air movement.
• Humidity.
• Clothing and PPE.
• The employee’s work rate and resulting metabolic heat.
• Difficulty Concentrating.
• Muscle Cramps.
• Heat Rash,
• Severe Thirst.
• Fainting.
• Fatigue.
• Dizziness.
• Nausea.
• Headaches and
• Heat Exhaustion.
• Improving natural or mechanical ventilation;
• Providing fans or air cooling;
• Ensuring air-conditioning systems operate effectively;
• Using blinds or reflective materials to reduce solar gain;
• Moving workstations away from direct sunlight;
• Insulating hot machinery, equipment or pipework; and
• Providing cooler areas for breaks.
• Scheduling physically demanding work for cooler parts of the day
• Introducing additional rest breaks.
• Rotating employees between hotter and cooler tasks.
• Reducing the duration of exposure.
• Allowing earlier or later start times where appropriate.
• Reducing unnecessary physical effort through mechanical aids and
• Temporarily modifying productivity expectations where heat significantly increases physical demands.
• Shaded rest areas.
• Opportunities to work in shade where practicable.
• Suitable drinking water.
• Adjusted working times.
• More frequent breaks during extreme conditions and
• Appropriate protection from sun exposure.
• Reviewing relevant risk assessments.
• Identifying roles particularly susceptible to heat exposure.
• Checking ventilation and cooling equipment.
• Ensuring drinking-water arrangements are adequate.
• Establishing arrangements for additional breaks.
• Considering flexible working arrangements.
• Briefing managers on symptoms of heat stress.
• Making sure employees know how to report concerns and
• Reviewing emergency and first-aid arrangements for heat-related illness.

For example, an office employee working at a desk in an air-conditioned environment will face very different risks from an employee undertaking strenuous manual work outdoors in direct sunlight.

Similarly, PPE can significantly increase the risk. Protective clothing may restrict the body’s ability to lose heat through sweating and evaporation. This is why employers should avoid relying on a particular temperature as their only trigger for action.

Understanding Heat Stress

Heat stress occurs when the body’s normal methods of controlling its internal temperature begin to struggle or fail.

The risk can increase where employees undertake physically demanding work, work in humid conditions, wear restrictive PPE or protective clothing, work close to heat-producing equipment, or spend extended periods in direct sunlight. Early recognition is particularly important. According to the HSE, symptoms associated with heat stress can include:

At the most serious end of the scale is heat stroke. Symptoms can include confusion, convulsions and loss of consciousness and the condition can be fatal if it is not recognised and addressed quickly.

Employers should therefore ensure employees and managers understand the warning signs and know how to raise concerns.

Assessing the Risk During Hot Weather

Employers should consider high temperatures as part of their workplace risk assessment arrangements rather than waiting until employees become unwell. The assessment should consider the circumstances of the work, including:

• The environment: Is the work indoors or outdoors? Is there direct sunlight, poor ventilation, high humidity or radiant heat from machinery or processes?
• The work activity: Does the role involve strenuous physical activity that generates additional body heat?
• Duration: How long are employees exposed to the conditions and do they have opportunities to recover somewhere cooler?
• PPE and clothing: Are employees required to wear equipment or clothing that restricts heat loss?
• The workforce: Could employees be more susceptible to the effects of heat?
• Welfare arrangements: Is cool drinking water readily available? Are appropriate rest areas provided?
• Existing controls: Are ventilation, shading, air conditioning or other controls available and working effectively?

The assessment should be reviewed when circumstances change, including during periods of unusually hot weather.

Practical Ways to Manage Above-Average Temperatures

The controls required will depend on the workplace and the level of risk. Employers should prioritise measures that reduce heat exposure rather than relying solely on employees to cope with it.

Improve the Working Environment

Where reasonably practicable, businesses can consider:

The HSE specifically recommends measures including fans, ventilation, shading, repositioning workstations and insulating sources of heat.

Change the Way Work Is Organised

Where environmental controls cannot adequately reduce exposure, working arrangements may need to change. This could include:

For higher-risk hot environments, the HSE recommends controlling both work rate and the length of exposure.

Hydration Matters

Dehydration is one of the most obvious risks associated with working in hot conditions. Employees should have ready access to suitable drinking water and should be encouraged to drink regularly rather than waiting until they feel extremely thirsty.

The HSE advises employers managing heat stress to provide cool water and encourage workers to drink frequently in small amounts. Drinking water is also a basic workplace welfare requirement.

Managers should therefore check that water supplies remain easily accessible, particularly for employees working outdoors, remotely or across large sites.

Don’t Forget Outdoor Workers

Employees working outside may face additional risks from direct sunlight and solar radiation. Consider providing:

Employers should also remember that hot weather can interact with other workplace hazards. Fatigue, reduced concentration and discomfort may increase the likelihood of mistakes when driving, operating machinery, working at height or undertaking safety-critical activities.

PPE and Hot Weather

PPE presents a particular challenge.

Employees should not simply remove required PPE because they are hot. Where PPE is necessary to control a significant workplace hazard, removing it may expose the employee to a greater immediate risk.

Instead, employers should consider whether the work can be reorganised, exposure reduced, additional breaks introduced or alternative suitable PPE provided.

The HSE notes that protective clothing and equipment can contribute to heat stress and that specialised cooling systems or breathable protective fabrics may be appropriate in some hot environments.

Listen to Employees

• Employee feedback can provide an important early warning that existing controls are no longer sufficient.
• If employees report uncomfortable temperatures, employers should not dismiss concerns simply because there is no statutory maximum temperature.

The HSE advises employers to reassess the risks where workers report or complain about uncomfortable temperatures, agree appropriate actions and act on the findings.

Consultation is particularly useful because employees carrying out the work are often best placed to identify where heat is becoming problematic and which controls are practical.

Preparing Before Temperatures Rise

Managing hot weather is much easier when arrangements are established before a heatwave arrives. Businesses should consider:

Having predetermined arrangements also helps managers make consistent decisions rather than improvising once temperatures have already become uncomfortable.

Key Message for Employers

• There may be no fixed maximum workplace temperature, but this should never be interpreted as meaning there is no responsibility to manage excessive heat.
• Employers must provide a reasonable working environment and assess and control risks arising from workplace temperatures.
• The appropriate response will depend on the environment, work activity, duration of exposure, humidity, clothing, PPE and individual circumstances.
• As temperatures rise, the most effective approach is therefore simple: assess the risk, listen to employees, introduce proportionate controls and act before uncomfortable conditions develop into a health and safety risk.