2026 is the first year in the UK weather record to reach 35°C in May, June and July. By 15 July Britain had already logged more days above 30°C than the whole of 1976. Four heatwaves before August.
There is still no legal maximum working temperature in Great Britain. You keep conditions "reasonable" and you assess heat like any other hazard. That is the whole of it, and it leaves the judgement with you.
That is changing. HSE is reviewing the Approved Code of Practice behind the Workplace (Health, Safety and Welfare) Regulations 1992, and ministers told Parliament in July that a public consultation is expected later this year. Trigger temperatures are on the table. So is a maximum recommended working temperature.
When it lands, nobody will ask whether you had a heat policy. They will ask what each worker knew, and when.
Your assurance data probably disagrees with your workforce
The University of Reading surveyed 307 managers and site workers at medium and large UK construction firms this year. 67% were concerned about heat affecting their health. 44% had already experienced a heat-related illness at work.
The finding that should worry you is the split between the two groups. Managers were confident the controls were in place and working. Workers were not. They pointed to access, communication and whether any of it held up on site.
That is the gap between what your assurance reporting tells you and what is true at the workface. It is not a controls problem. Water, shade and rest breaks are on most sites. It is a knowledge problem, and knowledge is the part nobody has been measuring.
Acclimatisation is a per-worker clock, not a policy
Heat tolerance is not something a worker either has or hasn't. It builds over roughly one to two weeks of graduated exposure, and it fades once the exposure stops.
UK construction starts further back than most. British summers are usually mild, so the workforce is rarely acclimatised when the heat arrives. A record-breaking May gives nobody time to adapt.
Then the clock keeps resetting. New starters, workers back from leave, agency operatives arriving on Monday morning: all of them are at the start line, on a site where everyone else has had three weeks to adjust. Most of them belong to a subcontractor, and you are assuring their competence without having delivered a word of their training.
A site-wide heat policy cannot see any of that. It is written once, for everyone, and it does not know who walked through the gate yesterday.
What you can actually evidence
Most heat awareness in UK construction happens once. A toolbox talk in May, a signing sheet, a folder.
That record answers one question: was this person told about heat stress at some point. On a 35°C Tuesday the question is different. Does this specific worker recognise the early symptoms, know their own risk factors, and know what to do when the person next to them stops sweating. If a third of the operatives on your site read English as a second language, add another question on top of that one.
The distance between those questions costs nothing on an ordinary day. It costs everything on the day someone goes down and your client, your insurer and possibly a coroner want to see what you held.
A signing sheet is a record of attendance. It has never been evidence of competence, and it will not survive a review of the ACOP that puts comprehension in scope.
Where LUMA1 fits
LUMA1 proves comprehension, not completion. A heat briefing becomes a clearance requirement for the site. The worker receives it on their phone, in their own language, before they start. LUMA1 records whether they understood it, not whether they signed for it.
That status sits in the same readiness profile as their card, their induction and their role briefings, across your own workforce and your supply chain. Cleared or Not Cleared, per worker, visible now rather than reconstructed after the event. That is how the system works, how GCL briefs every worker in their own language, and how Falco cascades a change across a supply chain with proof of understanding.
When the guidance changes, and it will, the contractors already holding comprehension evidence per worker will not have to build anything. They will export it.
A signature in May is not readiness in July.
Book 15 minutes and see what readiness evidence looks like on a live site.