A warehouse operative in Coventry clocks in at 7am to a building that will hit 34°C by midday. A line cook in Birmingham works a full service in a kitchen hovering near 40°C. A delivery driver in Bristol spends the afternoon in a cab with no functioning air conditioning. All three can be disciplined for walking off the job, and not one of them can point to a single statutory number that says the temperature is legally too high to continue. That gap, between rising summer temperatures and the absence of any maximum-temperature ceiling in UK law, sits at the centre of one of the most practically consequential unresolved questions in UK employment regulation.

The Trades Union Congress has called for a statutory indoor maximum of 30°C, lowered to 27°C for strenuous physical work. UNISON supports the same thresholds. Neither figure is law. Meanwhile the Health and Safety Executive, the statutory body responsible for workplace safety enforcement, continues to operate against a framework built around the word reasonable rather than a hard number. For HR professionals and for workers, this is not an abstract policy debate: it is a live operational problem that will only intensify as summer heatwaves become more frequent.

What the law actually says (and what it does not)

The governing instrument is Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992, which requires employers to maintain a temperature that is reasonable during working hours and to provide a sufficient number of thermometers for workers to check it. The Health and Safety Executive's Approved Code of Practice, published under the Health and Safety at Work Act 1974, adds a floor: a minimum of 16°C for sedentary work and 13°C where the work involves significant physical effort. There is no equivalent ceiling anywhere in the statutory framework. None.

In practice, reasonableness is assessed retrospectively: by an employment tribunal, by an HSE inspector following a complaint, or through a union grievance procedure. That approach works adequately when the weather is temperate. It becomes structurally inadequate when a sustained heatwave settles over a distribution centre for several days and no one, on either side of the employment relationship, can say with legal certainty whether 32°C indoors has crossed a threshold requiring action.

The TUC's proposed ceiling of 30°C (27°C for strenuous work) has traction as a campaigning benchmark, and UNISON has reinforced it by calling for employer action to begin at 24°C wherever possible. Until Parliament legislates or the HSE issues a revised Approved Code of Practice with explicit maximum figures, those numbers carry persuasive weight in a tribunal argument but no direct enforcement authority.

Who actually bears the heat

The workers most exposed to extreme workplace heat are rarely those with the strongest bargaining position. The heat-intensive sectors map closely onto the lower-paid segment of the UK labour market: warehousing and logistics, commercial kitchens, transport cabs, outdoor construction sites, laundries, and factories running metalwork or baking processes. Office-based workers, who more often have recourse to air conditioning, building management functions, and HR contact, are structurally better placed to escalate complaints effectively.

Unite the Union, which organises across manufacturing, logistics, and distribution, has persistently raised heat conditions as a hazard in member workplaces, particularly in large fulfilment centres where physical output targets and temperature extremes combine. The problem is compounded in sectors with a high proportion of agency or insecure-contract workers, who face greater informal pressure not to raise complaints.

Gig economy drivers and platform-based couriers occupy a particularly ambiguous position. Their working environment is defined by the vehicle they own or hire and the algorithm that routes them, not a fixed worksite for which a named employer carries a clear statutory duty of care. A self-employed courier working through a 35°C afternoon has fewer formal escalation routes than a directly employed warehouse operative whose employer has a site health and safety officer on shift.

For employees: what you can do right now

Even without a statutory maximum, workers have more leverage than the gap in the law might suggest. The duty on employers to assess risk and take reasonable steps to mitigate it is enforceable under the Workplace (Health, Safety and Welfare) Regulations 1992 and the broader employer duty under the Health and Safety at Work Act 1974. The absence of a ceiling does not mean the absence of obligation. The following steps translate that leverage into practical action.

• Document the temperature. A timestamped photograph of a thermometer reading, noting the location and time, is straightforward evidence. Build a record across several days if the problem is recurring: pattern evidence carries considerably more weight in a grievance or tribunal than a single data point.
• Raise it in writing. An email to a line manager or HR contact, rather than a verbal mention, creates a traceable record. Ask specifically what mitigation measures are in place and when the risk assessment was last reviewed.
• Recognise the symptoms of heat exhaustion. Dizziness, nausea, cramps, and heavy sweating are physiological responses that warrant stopping work. They are not a reason to push through. Hydrate, move to a cooler area, and report the incident formally.
• Involve your union where one exists. Collective grievances, particularly through Unite or UNISON in heat-intensive sectors, move through workplace processes faster than individual complaints and carry more weight with management.
• Take care before leaving the site. Refusing to work without first formally raising the issue creates disciplinary risk. Section 44 of the Employment Rights Act 1996 provides protection for workers who leave a workplace or refuse to return to it in circumstances of serious and imminent danger that they could not reasonably have been expected to avert. The bar is not trivial: the danger must be imminent, not merely uncomfortable. ACAS (Advisory, Conciliation and Arbitration Service) provides a free helpline and can advise on whether your specific circumstances are likely to meet that threshold before you act.

If you want to understand how your employer's approach to heat compares with others in your sector, verified reviews from current and former employees can surface patterns quickly. When multiple workers at the same site report the same broken ventilation or the same management non-response, a pattern becomes visible that individual experience alone cannot establish.

For HR and employers: a liability gap, not merely a policy gap

Reading the absence of a statutory maximum temperature as the absence of any obligation is a common mistake, and it is proving an increasingly costly one. The Workplace (Health, Safety and Welfare) Regulations 1992 and the Health and Safety at Work Act 1974 impose a present duty, not a conditional one. What qualifies as reasonable in 2026, against a background of more frequent and more intense summer heatwaves, is a moving standard. An approach that would have satisfied an HSE inspection in 2014 may not withstand scrutiny today in a setting where workers are presenting with heat-related illness.

The CIPD (Chartered Institute of Personnel and Development), whose membership covers the majority of senior HR practitioners in the UK, advises that health and wellbeing risk assessments should be reviewed in light of changing climate patterns and that heat specifically should appear as a named hazard in workplace risk frameworks rather than being absorbed into a general catch-all category. Organisations that have integrated heat management into their annual risk review cycle are better positioned, both practically and legally, than those treating it as a one-off seasonal concern.

If binding statutory limits arrive, the TUC's proposed 30°C / 27°C figures are the most credible anchor for what those limits would look like. Organisations already operating to those thresholds will face minimal adjustment costs. Those that do not will face retrofit expenditure, potential operational disruption during peak summer periods, and the reputational and legal consequences of being on the wrong side of an enforcement action.

A defensible HR posture in this environment has five identifiable components:

1. A written heat policy. This should specify trigger temperatures, a graduated menu of mitigation steps, and a clear escalation path. The absence of any written policy is itself a liability signal in any subsequent tribunal or HSE investigation.
2. A risk assessment that names heat as a hazard. Generic risk assessment documents that do not address extreme heat are increasingly difficult to defend. The assessment should reference seasonal temperature forecasting and specify what operational responses apply at each temperature level.
3. Concrete mitigation measures. Hydration provision, relaxed dress codes, task rotation, scheduled rest periods in cooler areas, shift-time adjustments during forecast heatwaves, and mechanical ventilation upgrades where site design permits. These should be planned before the heatwave, not improvised during it.
4. A clear non-retaliation commitment. Workers who report unsafe heat conditions should face no adverse consequences. Tribunal records consistently lengthen when this principle is breached, and the reputational effects outlast the proceedings themselves.
5. Front-line manager training. The decision to halt work on a hot shift is typically made by a supervisor, not a senior HR manager. That supervisor needs to recognise heat exhaustion symptoms, understand when the section 44 ERA 1996 threshold is likely to be relevant, and know how to log incidents correctly.

The business case for acting before compulsion is grounded in measurable outcomes. Research cited by the HSE and by occupational health bodies indicates that cognitive performance and physical productivity begin to fall at indoor temperatures above 28°C. Sick leave rates increase following sustained heatwaves. Recruitment and retention in heat-intensive operations tighten when workers in a tight labour market can compare conditions across employers. Sustained physical discomfort is a documented contributor to front-line operational burnout, independent of workload intensity.

Where UK regulation goes next

The political route to a statutory maximum temperature is not straightforward. Successive UK governments have defaulted to guidance rather than hard limits, and employer representative bodies have consistently resisted a single number on the grounds that sector variation makes one figure inappropriate across all working environments. The union argument, pressed by TUC and UNISON, is precisely that the absence of a number shifts the burden of risk assessment onto individual workers who are least equipped to bear it.

What is changing is the underlying data. Heatwaves that were once-a-decade events are becoming regular features of UK summers, with the Met Office and ONS (Office for National Statistics) mortality data both pointing to measurable health impacts on working-age adults during sustained high-temperature periods. Each heatwave season generates fresh tribunal claims, fresh HSE inspection activity in heat-sensitive sectors, and fresh political pressure on a regulatory framework that has not materially changed since the 1992 Regulations came into force.

For workers, the practical position is to document conditions, raise concerns formally, and use collective channels through Unite, UNISON, or other recognised trade unions where available. For HR teams and employers, the calculation is direct: operating to the TUC's proposed thresholds now, before any statutory obligation arrives, is considerably less expensive than retrofitting under an enforcement deadline, and far less expensive than defending a claim arising from a worker who required medical treatment on a shift where the temperature was recorded at 36°C and no heat policy existed. The legal grey zone narrows incrementally through tribunal decisions and HSE enforcement activity. Acting inside it is a choice; being caught inside it when it finally closes is a much more costly one.