Heat in the Workplace

Employer legal duties, first aid requirements, and practical heat management for HR, health and safety, and line managers 

On 25 and 26 May 2026, the UK broke its all-time May temperature record twice in two days, with Kew Gardens reaching a provisional 35.1°C. The Met Office has confirmed that extreme heat events of this magnitude are now roughly three times more likely than they were before human-caused climate change took effect.

For most UK employers, workplace heat has historically been a minor seasonal inconvenience. That framing is no longer adequate. Extreme heat is becoming a recurring feature of the UK working year. The legal framework governing employer responsibility has not needed to change substantially because existing duties already apply to heat risk.

This guide is structured in two parts. The first covers the current legal position clearly and practically. The second covers the practical measures employers are expected to take, including first aid response. Both are relevant to HR managers, health and safety leads, and line managers with responsibility for teams.

Part One: The Legal Position 

There Is No Maximum Workplace Temperature. That Does Not Mean No Duty.

The question employers most frequently ask during a heatwave is whether there is a legal maximum working temperature. There is not. The Health and Safety Executive (HSE) takes the position that no meaningful upper limit can be set across all workplaces because some industries, such as bakeries, foundries, and glass manufacturing, operate at high temperatures as a matter of course. Setting a single threshold that applied universally would either be unenforceable in those environments or would shut down large parts of the economy.

This position is frequently misread as meaning that employers have no specific duty in hot weather. That is incorrect, and it is a misreading that creates genuine legal exposure.

The Legislative Framework

Four pieces of legislation are directly relevant to employer duties in hot weather. Each imposes distinct obligations.

Employer Legal Duties: Heat in the Workplace

What ‘Reasonable Temperature’ Actually Means

Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires a ‘reasonable’ indoor temperature. The Approved Code of Practice states that the temperature should provide ‘reasonable comfort without the need for special clothing’. No specific maximum is defined, but the standard is not passive.

When HSE inspectors assess whether a workplace temperature was reasonable, they consider the full picture: whether a risk assessment was carried out, whether control measures were implemented, whether workers raised concerns, and what action was taken in response. An employer who does nothing during a heatwave and subsequently has a worker suffer heat exhaustion or heatstroke is in a significantly worse position than one who implemented appropriate measures even if those measures did not fully prevent harm.

The TUC has campaigned for a statutory maximum of 24°C, and in June 2025 the House of Lords debated whether HSE should conduct a fresh review of the evidence. The Labour manifesto in 2024 included a commitment to modernise heat guidance. Legislative change remains possible. Whether or not a maximum is eventually introduced, the existing framework already requires active management of heat risk.

The Risk Assessment Obligation

Regulation 3 of the Management of Health and Safety at Work Regulations 1999 requires employers to carry out a ‘suitable and sufficient’ risk assessment of all foreseeable hazards. Hot weather is a foreseeable hazard. An employer who has not assessed heat risk cannot credibly claim to have met their duty of care.

A heat risk assessment for workplace purposes should identify which roles, locations, or tasks create elevated heat risk, what control measures are in place, whether those measures are adequate under a range of temperature conditions, and which workers may be at greater risk due to health conditions, medication, or lack of acclimatisation. New starters deserve particular attention: the body takes time to adjust to working in heat, and acclimatisation typically takes up to two weeks.

The assessment is not a one-time document. When conditions change significantly, including during a heatwave or when the UKHSA issues a heat-health alert, the assessment should be reviewed and control measures adjusted accordingly.

First Aid Legal Requirements

The Health and Safety (First Aid) Regulations 1981 require employers to provide adequate and appropriate equipment, facilities, and trained personnel to ensure employees receive immediate assistance if they are injured or become ill at work. This obligation applies to heat illness. 

What constitutes adequate first aid provision is determined by the size and nature of the organisation, the hazards present, and the number of employees. During a heatwave, the risk of heat illness rises materially. An employer whose first aid provision was adequate under normal conditions should consider whether it remains adequate when temperatures are exceptional. 

Specifically, the designated first aider or appointed person must be capable of recognising and responding to heat exhaustion and heatstroke. These are not niche or specialist conditions during a UK heatwave in 2026: they are foreseeable emergencies. If first aiders are not confident recognising and responding to heat illness, employers should treat that as a gap in their current first aid arrangements.

Part Two: Practical Heat Management

What Employers Are Expected to Do

HSE guidance identifies a range of practical control measures that employers should implement when heat presents a risk. Employers do not need to apply every measure in every workplace, but they do need to show that heat risk has been assessed and suitable controls have been considered and implemented. These are the measures HSE inspectors expect to see evidenced in a proportionate response to a foreseeable hazard. 

Environmental controls

• Provide adequate ventilation. Open windows, use fans, and deploy air conditioning where available.
• Close blinds and curtains on south and west-facing windows during peak sun hours to reduce solar heat gain.
• Reduce heat-generating equipment use where practicable.
• Identify cooler areas of the workplace and make them accessible as rest spaces.

Work pattern adjustments

• Schedule physically demanding or outdoor work during cooler parts of the day, typically before 11am or after 3pm.
• Introduce additional rest breaks in cool areas and rotate tasks to reduce individual heat exposure.
• Consider whether any work can be deferred until conditions improve.
• Do not penalise workers who raise concerns about thermal comfort or request breaks.

Hydration

• Provide free access to cool drinking water at all times. This is an explicit expectation in HSE guidance.
• Actively encourage workers to drink regularly, not just when thirsty. By the time thirst develops, dehydration is already present.
• Avoid relying solely on vending machines or paid options: access should be free and without barriers.

Communication

• Brief line managers on the signs and symptoms of heat exhaustion and heatstroke before and during heatwaves.
• Communicate the heat management plan to all staff. Workers should know where to find water, where to rest, and who to report concerns to.
• Monitor UKHSA heat-health alerts and adjust measures accordingly when alerts are upgraded.

Employer Heat Action Checklist

Recognising and Responding to Heat Illness at Work

Line managers and first aiders must be able to distinguish between stages of heat illness, because the appropriate response is different at each stage. The key distinction is between heat exhaustion, which responds to first aid, and heatstroke, which is a medical emergency requiring 999. 

Heat exhaustion

Heat exhaustion occurs when the body is under severe thermal strain but has not yet failed to regulate its core temperature. Signs include heavy sweating, pale and clammy skin, headache, dizziness, nausea, muscle cramps, and a rapid weak pulse. The affected worker is usually still conscious and able to communicate.

Heatstroke

Heatstroke is a life-threatening emergency. Core temperature is dangerously high, typically above 40°C. The body’s thermostat has failed. The most critical warning sign is skin that becomes hot and dry after a period of heavy sweating. Confusion, agitation, loss of coordination, seizure, or unconsciousness may follow rapidly.

What Line Managers Need to Do

Legal responsibility rests with the employer, but line managers are the operational interface. Their decisions during a heatwave directly affect both worker safety and the organisation’s compliance position. Managers should be briefed clearly on the following:

•  You are expected to act on heat concerns raised by workers. Dismissing complaints about temperature as oversensitivity is not a defensible position if a worker subsequently becomes ill.
• If a worker appears unwell during hot weather, do not wait for them to ask for help. Ask directly, act promptly.
• Ensure breaks are actually taken, not pressured away. Workers who skip rest breaks in high heat face elevated risk.
• Do not discourage workers from removing excess clothing or using fans. Practical cooling is not a discipline issue.
• If you are uncertain whether a worker needs medical attention, call 999. The consequences of under-responding to heatstroke are severe and irreversible.

Record Keeping and Documentation

In the event of a heat-related illness incident, the employer’s documentation will be scrutinised. The following records are relevant to both HSE investigation and civil claims: 

• The current heat risk assessment and the date it was last reviewed.
• Evidence that control measures were communicated to staff and line managers.
• Records of UKHSA heat-health alert monitoring and any operational changes made in response.
• The first aid incident report, including time of onset, symptoms, actions taken, and outcome.
• Training records confirming that first aiders were trained in heat illness recognition and response.

An organisation that can demonstrate a systematic, documented approach to heat risk management is in a materially better position than one that cannot, regardless of the outcome of any individual incident. Documentation is not bureaucracy in this context: it is the evidence of compliance.

Workplace heat is a risk management responsibility, not a seasonal inconvenience. The legal framework is clear, the climate trend is unmistakeable, and the consequences of inadequate preparation fall on both the worker and the organisation.

This guide focuses on the employer's legal position and operational responsibilities. For a detailed clinical guide to heat-related illness, including how to recognise and treat dehydration, heat exhaustion, and heatstroke, and a dedicated section on children and babies, the full public guide is available here: https://blog.constellationtraining.co.uk/heat-related-illness-guide/

Constellation Training provides FAIB-accredited first aid training for workplaces throughout the UK, including in-house courses for organisations that want their first aiders confident with realistic workplace emergencies, including heat-related illness. Details of upcoming open and in-house options are available on our website.

Discuss Your Organisation’s Training Needs

 Constellation Training provides FAIB-accredited first aid training for workplaces throughout the UK, including in-house courses for organisations that want their first aiders confident with realistic workplace emergencies, including heat-related illness. Details of upcoming open and in-house options are available on our website.

References

^[1]  Health and Safety Executive. ‘Temperature in the workplace’. Available at: www.hse.gov.uk/temperature

^[2]  Workplace (Health, Safety and Welfare) Regulations 1992, Regulation 7 and Approved Code of Practice. Available at: www.legislation.gov.uk

^[3]  House of Lords debate on UK extreme heat preparedness, June 2025. Hansard. Available at: hansard.parliament.uk. Labour Party General Election Manifesto 2024, health and safety commitments. Available at: labour.org.uk/change

^[4]  Management of Health and Safety at Work Regulations 1999, Regulation 3. Available at: www.legislation.gov.uk

^[5]  Health and Safety (First Aid) Regulations 1981. Available at: www.legislation.gov.uk

^[6]  Health and Safety Executive. ‘Heat stress in the workplace’ (INDG451). Available at: www.hse.gov.uk/pubns/indg451.htm

^[7]  Health and Safety at Work etc. Act 1974, Section 2(1). Available at: www.legislation.gov.uk

^[8]  Met Office. ‘UK May and spring temperature record provisionally broken for second day in a row’. May 2026. Available at: www.metoffice.gov.uk