UK Red Heat Warning: What Employers Must Do Right Now

The Met Office has issued a rare Red extreme heat warning for parts of England and Wales, running from 9am Wednesday 24 June until 9pm Thursday 25 June. Temperatures are forecast to hit 36–38°C, with some areas potentially touching 40°C. An Amber warning covers Yorkshire and other parts of the country not under Red.

The HSE has issued an active reminder to employers today. Heat is legally classified as a workplace hazard. The fact there is no maximum legal working temperature in the UK does not protect you if a worker collapses on your watch.

Here is what you need to do.

Shift Timing

For outdoor and physically demanding work, this is the single most effective control measure available to you right now.

• Start at 5am or 6am to get the bulk of the work done before temperatures peak
• Aim to finish all heavy outdoor work by 1pm–2pm on Wednesday and Thursday
• Move admin, toolbox talks, equipment checks, and vehicle maintenance to the hottest part of the afternoon
• Construction firms across Europe are already operating on dawn starts this week — this is a proven, practical approach, not an overreaction

Rest Breaks in Shade

Do not leave this to workers to self-manage. By the time someone feels rough enough to stop, the warning signs have already been missed.

• Build a rest schedule: a 10-minute break in shade every 45–60 minutes during heavy work above 30°C is reasonable
• If your site has no natural shade, create it — pop-up gazebos, vehicle shade, or a shaded rest area
• Encourage workers to remove PPE during rest breaks — this is not optional, it is a meaningful control measure

Hydration

• Provide free, readily accessible cold water on every site — HSE guidance is explicit on this
• The target during heavy physical work in heat is roughly 250ml every 20 minutes
• Avoid caffeine and alcohol before and during shifts — both accelerate dehydration
• For workers sweating heavily over extended periods, electrolyte sports drinks are more effective than water alone

PPE

Review whether full PPE is necessary during peak heat periods this week.

• Where it can safely be lightened (e.g. a lighter base layer instead of a heavy overall), make that adjustment
• Workers must be encouraged — and given permission — to remove PPE during rest breaks
• If a worker in full PPE is sitting in a south-facing van during their lunch break, that is not rest — that is continued heat exposure

Indoors and In Vehicles

• Open windows early morning before temperatures rise, then close them and use blinds during peak heat to trap cooler air inside
• Position workstations away from south-facing windows and direct sunlight
• Fans circulate air but do not cool it — once ambient temperature exceeds body temperature (~37°C), fans can make conditions worse
• Workers waiting in vans or vehicles should never sit in direct sun with the engine off — provide shaded waiting areas

Know Who Is Most at Risk

Some workers are significantly more vulnerable than others:

• Workers over 65
• Workers on certain medications (diuretics, antidepressants, antipsychotics)
• Workers in hot process roles (welding, catering, bakeries, foundries)
• Outdoor workers in physically demanding trades — roofing, groundwork, landscaping, construction, utilities
• New starters and workers returning from leave — the body takes 7–14 days to acclimatise to heat. Someone back from two weeks' holiday during a Red warning is at their highest risk point in their first week back

Recognise the Symptoms

Heat exhaustion (act fast — not yet an emergency): Heavy sweating, pale clammy skin, dizziness, headache, nausea, muscle cramps, weakness

Heat stroke (medical emergency — call 999 immediately): Confusion, slurred speech, loss of consciousness, hot dry skin (sweating has stopped), very high body temperature

The critical distinction: if sweating has stopped and the person is confused, that is heat stroke. Do not wait. Call 999.

What Managers Should Do Today

1. Check the Met Office — confirm which warning level applies to each of your sites
2. Brief your teams this morning — a verbal toolbox talk takes five minutes and covers symptoms and what to do
3. Adjust start and finish times where operationally possible
4. Confirm water supply on every site before tomorrow morning
5. Identify your vulnerable workers — new starters, older workers, anyone on medication
6. Make clear that workers can say they feel unwell — heat illness can come on fast, and workers often push through when they should not

The Legal Position

There is no maximum legal working temperature in the UK. The Workplace (Health, Safety and Welfare) Regulations 1992 require temperatures to be "reasonable," but that threshold is undefined for heat. What is clear is that heat is a hazard, and employers are legally required to assess and control it under the Health and Safety at Work Act 1974 and the Management of Health and Safety at Work Regulations 1999.

In May 2026, the Climate Change Committee recommended the Government commit to a national maximum workplace temperature. That recommendation has not yet been legislated, but the direction of travel is clear.

Failure to assess and control heat as a hazard is a legal exposure — not a grey area.

If you need help reviewing your hot weather procedures, risk assessments, or toolbox talks for this week, visit www.safecompli.co.uk or get in touch directly.