Working in the heat: hot weather toolbox talk and heat protocol

When temperatures climb, the risks on site climb with them: dehydration, heat exhaustion, loss of concentration and more mistakes. UK summers are getting hotter, and a heatwave can arrive with only a few days' warning.

This guide explains what UK law says about working in hot weather, the signs of heat illness, what to put in a heat protocol and a heatwave plan, and how to protect people working outdoors, indoors in hot buildings and in care. It ends with the points to cover in a hot weather toolbox talk and how to get it to everyone before the heat hits.

UK law on working in hot weather

There is no maximum working temperature in UK law. That surprises many people, but it does not mean "anything goes". Several duties apply:

• Health and Safety at Work etc. Act 1974: you must protect workers' health and safety so far as is reasonably practicable, and heat is a health risk like any other.
• Management of Health and Safety at Work Regulations 1999: your risk assessment (regulation 3) must cover heat where it is a significant risk, with extra attention for new and expectant mothers and young workers.
• Workplace (Health, Safety and Welfare) Regulations 1992, regulation 7: the temperature inside workplaces must be reasonable during working hours. Regulation 22 requires an adequate supply of drinking water.

HSE guidance on heat stress and thermal comfort explains how to assess the risk. What counts as reasonable depends on the work: heavy physical work, PPE, humidity, radiant heat from machines or the sun, and the people doing it all play a role.

Heat-health alerts

The UK Health Security Agency and the Met Office issue heat-health alerts (yellow, amber and red) and the Met Office issues extreme heat warnings. Use them as triggers in your heat protocol, so action starts automatically rather than when someone happens to notice.

When does heat become a risk at work?

Risk rises with a combination of factors, not just the thermometer:

• High air temperature and humidity (sweat cannot evaporate)
• Direct sun or radiant heat from ovens, furnaces, machinery or a hot roof
• Heavy physical work
• PPE or protective clothing that traps heat
• Little air movement
• Workers who are not used to the heat: new starters, people back from leave, the first hot days of the year
• Personal factors: age, pregnancy, some medical conditions and medicines

Signs of heat illness: what everyone should recognise

What you see or feel	What it may be	What to do
Thirst, tiredness, headache, dark urine	Dehydration	Drink water, rest somewhere cool
Painful muscle cramps, heavy sweating	Heat cramps	Stop, cool down, drink water or a rehydration drink
Dizziness, nausea, pale clammy skin, weakness	Heat exhaustion	Move to a cool place, lie down with legs raised, cool the skin, give water, stay with them
Confusion, hot skin, stopped sweating, collapse, seizure	Heatstroke: life-threatening	Call 999, cool them fast with cold water and air movement, do not leave them alone

Heat exhaustion can turn into heatstroke quickly. If someone does not improve within 30 minutes of cooling down, treat it as an emergency.

What a heat protocol should cover

A heat protocol sets out in advance what happens when it gets hot, so supervisors do not have to improvise. Build it on your risk assessment and include:

1. Triggers: which forecast, alert level or measured temperature activates which measures, and who decides.
2. Water and rest: cool drinking water close to the work, more frequent breaks in shade or a cool room, longer as the heat increases.
3. Working hours: moving heavy work to early morning, avoiding the hottest part of the day, flexible start times.
4. Task planning: rotating heavy tasks, sharing lifting, postponing non-urgent hot work.
5. Shade and cooling: gazebos, canopies, fans, ventilation, air conditioning in rest areas, insulated or shaded vehicles.
6. Clothing and PPE: light, breathable clothing where safe; never removing essential PPE, but adding breaks when PPE traps heat.
7. Buddy system: nobody working alone in extreme heat, colleagues checking on each other.
8. Vulnerable workers: new and expectant mothers, young workers, people with relevant health conditions, and those not yet used to the heat.
9. First aid and emergency: who recognises the signs, how to cool someone, when to call 999.
10. Communication: how you warn everyone, in their own language, before the heat arrives.

Heatwave plan: what employers should arrange

A heatwave is a test of your protocol. In the days before and during a hot spell:

• Check the forecast and alerts daily and activate the protocol on time.
• Make sure water, shade and cool rest areas are actually in place on every site.
• Review rotas and start times with supervisors.
• Check in with vulnerable workers individually.
• Send a short hot weather toolbox talk to everyone, including drivers, mobile workers and people who start tomorrow.
• Record who has received and understood it.

The real challenge: reaching everyone in time

A notice on the canteen wall does not reach the driver who leaves at 6am. An email does not reach the groundworker on site all day. The people most at risk in a heatwave are often the hardest to reach. A heat instruction that nobody reads is not a control measure, it is a document. Send it to their phone the day the alert is issued.

Working outdoors in the sun

For construction, groundworks, landscaping, road and utility work:

• Plan heavy work early in the day and avoid it around midday and early afternoon.
• Drink before you feel thirsty: small amounts often, water rather than energy drinks.
• Work in shade where possible, or create it with canopies.
• Cover up: long sleeves in light fabric, a helmet sun brim or neck flap, and high-factor sunscreen on exposed skin. Skin cancer from UV is a long-term risk HSE asks outdoor workers to take seriously.
• Take extra care with work at height when anyone feels dizzy or unwell.
• Do not take off PPE because it is hot. Talk to the supervisor about making the work cooler instead.

Heat indoors: warehouses, production halls and kitchens

Under a steel roof, next to ovens or among running machines, it can get hotter inside than out, and humidity from steam or a busy shift makes it harder for the body to cool down. "It's only indoors" is exactly the trap.

• Increase air movement: ventilation, extraction, fans, opening doors where safe.
• Shield people from radiant heat sources and insulate hot pipes and surfaces.
• Provide a cooler rest area and allow more frequent breaks.
• Spread heavy tasks across the shift.
• Monitor temperatures in the hottest spots and act on your protocol triggers.
• Remember that hygiene clothing and PPE in food production and kitchens trap heat too.

Heat in care work

Care workers face a double load: physically demanding work, and clients who are often most vulnerable to heat. Older people feel thirst less, and some medicines affect fluid balance. People with dementia may not be able to say they are too hot.

• For clients: offer drinks actively and often, keep rooms cool (close curtains on the sunny side, ventilate at night), and watch for confusion, drowsiness, dark urine or reduced urine. Raise concerns with the nurse, GP or pharmacist.
• For carers: drink regularly yourself, take breaks somewhere cool, share heavy transfers, and plan home visits so the hardest tasks are not at the hottest time.

Hot weather toolbox talk: what to cover

Keep it short and practical. In hot weather, speed and clarity matter more than detail.

1. Why heat is a safety risk, not just discomfort.
2. The signs of dehydration, heat exhaustion and heatstroke.
3. Drink before you are thirsty, and where water is on this site.
4. Breaks, shade and the cool rest area.
5. Sun protection and keeping PPE on.
6. Look out for each other, and how to report feeling unwell.
7. What to do in an emergency: cool them down and call 999.

Finish with two or three questions to check understanding. You can find more seasonal topics in our toolbox talk topics library, and the winter counterpart in our cold weather toolbox talk. For PPE in the heat, see mandatory PPE at work.

Frequently asked questions

Is there a maximum temperature for working in the UK?

No. The law requires a reasonable temperature indoors and a risk assessment for heat, but sets no maximum. HSE guidance helps you decide when action is needed, based on the work, the environment and the people.

Can workers go home when it is too hot?

There is no automatic right to stop work because of heat. But you must control the risk. If you cannot make the work safe, you need to change, postpone or stop it, and workers can raise serious and imminent danger with you.

Do employers have to provide water in hot weather?

Yes. The Workplace Regulations 1992 require wholesome drinking water to be readily available at all times. In hot weather, make sure it is close to the work and cool.

What is the minimum temperature at work?

HSE's Approved Code of Practice suggests at least 16°C indoors, or 13°C for strenuous work. There is no equivalent maximum.

Who is most at risk in a heatwave?

People doing heavy work, those wearing heat-trapping PPE, workers not used to the heat, new and expectant mothers, young workers and people with certain health conditions or medicines.

Reach every worker before the heat with E-lia

With E-lia, you send a hot weather toolbox talk via WhatsApp the moment an alert is issued: straight to every worker's phone, no app, no login, in their own language. It takes 5 to 8 minutes, ends with a short knowledge check, and your dashboard shows who has completed it, so you can follow up with anyone who has not. Learn more about toolbox talks via WhatsApp.