Sadiq Khan backs a 40C workplace cap as UK heatwaves push unions to demand change

Mayor of London Sadiq Khan has backed union calls for a maximum workplace temperature, as pressure mounts on the UK government to update health and safety rules for a hotter era. The urgency is not theoretical. The source notes that in some workplaces, temperatures have climbed above 40C, forcing real-time disruption when people struggle to cope.

Khan’s backing lands at a moment when extreme heat is already battering core services. The source says the heat has left people struggling to cope as temperatures in some workplaces reach above 40C, and that it has contributed to thousands of schools closing and to hospital and transport systems breaking down. In other words, this is not just a workers’ rights debate. It is a continuity and resilience debate, with safety rules at the center.

To understand why a workplace temperature cap is suddenly politically loud, it helps to know how UK workplace health and safety regulation typically works. Employers are expected to manage risks and protect workers from hazards. Extreme heat is a hazard that can rapidly change throughout a shift, affecting physical capacity, concentration, and the risk of heat-related illness. Unions are effectively arguing that the current framework has not kept pace with how often heatwaves now strike, and that the rules need updating to match the lived reality of more frequent extreme temperatures.

When unions push for a maximum workplace temperature, the practical goal is straightforward: set a measurable threshold that triggers action. That threshold can drive everything from work-rest schedules to air-conditioning requirements, hydration protocols, staffing plans, and the conditions under which outdoor or poorly ventilated sites must pause operations. Even if the exact mechanism is still being argued politically, the direction of travel is clear in the source: more frequent heatwaves are raising the stakes, and workers and their representatives want protections that are enforceable, not just aspirational.

The second-order pressure is that employers do not just face compliance risk, they face operational knock-on effects. The source points to thousands of school closures and breakdowns in hospital and transport systems, all tied to extreme heat. That combination matters for workplaces because it can cascade into labor availability, caregiving burdens, and commuting challenges. If transport systems break down during heat events, employees may show up late, fatigue faster, or avoid hazardous routes. If schools close, parents may be absent or unable to maintain normal schedules. Employers then have to manage both the physical safety risks and the staffing instability risks during the same event.

There is also a board-level lens here. When regulatory debates move from “safety best practices” to “what the rules must be,” compliance becomes a governance issue. Boards typically want to know: what is the exposure, what are the triggers, and what is the readiness plan? A maximum workplace temperature policy, once implemented or even proposed, can reshape how risk is assessed across facilities, suppliers, and contractors. It can also create a reputational dimension. Companies that appear unprepared during heatwaves may face public scrutiny, while companies that demonstrate readiness can gain trust with workers and local stakeholders.

Khan backing union calls adds another layer of political leverage. The mayor of London is a prominent voice in a country where heat impacts urban infrastructure and public services directly. The source frames his support as part of the growing pressure on the government to protect workers from the impact of repeated heatwaves across the UK. For policymakers, union pressure can accelerate legislative or regulatory updates. For employers and executives, that same acceleration means timelines can compress. What looked like “future guidance” can become “immediate requirement,” especially if heatwaves keep delivering high-impact outcomes like closures and system breakdowns.

For peers in similar roles, the strategic stakes are simple: treat workplace heat as an enterprise risk, not only a health and safety checkbox. The source signals the direction with a concrete reference point above 40C in some workplaces, plus the broader societal impacts on schools, hospitals, and transport. If a maximum temperature cap becomes the regulatory norm, companies that prepare early will reduce disruption and protect workers. Companies that wait for clearer rules may scramble when temperatures climb and systems fail at the same time.