What's the Maximum Legal Working Temperature in the UK?

There isn't one.

No number. No threshold. Nothing in law that says "above this temperature, work stops." Most employers — and a surprising number of people who work in health and safety — don't know that.

With this week's heatwave fresh in the memory and summer still ahead, it's worth understanding what the law actually says, what it doesn't say, and what your duty is in the gap between those two things.

What the Law Actually Says

The Workplace (Health, Safety and Welfare) Regulations 1992 require employers to maintain a "reasonable" temperature in indoor workplaces. The accompanying Approved Code of Practice sets a minimum — 16°C for sedentary work, 13°C for work involving physical effort — but sets no upper limit.

For outdoor workers, the Regulations don't directly apply. Instead, the duty falls back on the general framework: the Health and Safety at Work Act 1974, which requires employers to ensure, so far as is reasonably practicable, the health, safety and welfare of their employees. And the Management of Health and Safety at Work Regulations 1999, which require employers to assess and control risks — including thermal risk.

Why There's No Maximum Temperature

The reason there's no fixed upper limit isn't an oversight. It's because what counts as "dangerous heat" varies enormously depending on the work. A factory worker doing heavy lifting in 28°C is in a very different situation from an office worker at the same temperature. A roofer in direct sunlight in 32°C, wearing PPE, doing physical work, is in a different situation again.

The law asks you to assess and control the risk — not just check a thermometer.

What This Means for Your Business

The absence of a maximum temperature doesn't reduce your duty. It arguably increases it, because you can't point to a number and say "we're compliant." You have to think about it.

For most businesses, managing heat stress risk means:

Risk assessment: Thermal comfort needs to be treated as a named hazard. If your risk assessment doesn't mention it, it's incomplete — particularly for outdoor trades, physical work, or environments without ventilation or air conditioning.

Rest breaks: Workers exposed to high temperatures need adequate rest breaks in a cooler area — shade, a vehicle cab with air conditioning, or an indoor space. This should be planned in advance, not improvised when someone starts feeling unwell.

Hydration: Cold drinking water should be available and accessible. Workers doing physical work in the heat need more than a water bottle they might have remembered to bring.

Job rotation: Where possible, rotating workers between tasks — particularly between high-exposure outdoor work and lower-intensity indoor or shaded work — reduces cumulative heat exposure.

Start times: During prolonged hot weather, adjusting start and finish times to avoid peak heat (typically 11am–3pm) is a practical and proportionate control measure. It doesn't require a policy change — it requires a conversation.

Monitoring: On very hot days, supervisors should be watching for signs of heat stress: unusual fatigue, confusion, headache, nausea, or excessive sweating. Heat stroke can develop quickly and is a medical emergency.

The Bigger Picture

Sustained heat doesn't just cause heat-related illness. It affects concentration, reaction time and decision-making — which raises the risk of everything else going wrong on site. A roofer who is fatigued from the heat is more likely to make a mistake at height. A driver who is dehydrated has impaired judgement.

Heat is a hazard that interacts with other hazards. It should be in your risk assessment not just as a standalone item but as a factor that affects the controls you have in place for other risks.

One Thing Worth Knowing

There is currently a campaign — backed by several unions and workplace safety organisations — for the introduction of a legal maximum working temperature in the UK. Whether that becomes law or not, your obligations under the existing framework are clear: assess the risk, put controls in place, and protect your workers.

The law not having a number doesn't mean you don't have to act. It means you have to think.

If your risk assessments don't currently include thermal comfort as a named hazard, SafeCompli's trade-specific safety packs are a practical starting point — pre-written, trade-specific, and ready to edit.

Visit www.safecompli.co.uk