Summer Heat in the Workplace — Your Legal Obligations (Before Everyone Melts)

Every summer, the same question circulates around offices, warehouses and factories across the UK: "Is it too hot to work?" Employees start Googling "maximum workplace temperature UK" and sharing articles that claim there's a legal limit. Social media fills up with people insisting it's illegal to work above 30°C.

The disappointing truth? There is no maximum workplace temperature in UK law. But that doesn't mean employers can sit in their air-conditioned office while their workers swelter. The legal obligations are real — they're just not as simple as a single number.

What the Law Actually Says

The Workplace (Health, Safety and Welfare) Regulations 1992 require that the temperature in workplaces during working hours is "reasonable." That's it. No specific number. The Approved Code of Practice suggests a minimum temperature of 16°C for sedentary work and 13°C for physical work, but there's no equivalent maximum.

However, the general duty under the Health and Safety at Work Act 1974 requires employers to ensure, so far as reasonably practicable, the health, safety and welfare of employees. If extreme heat is making people ill, causing heat stress, or impairing their ability to work safely, the employer has a duty to act.

The Management of Health and Safety at Work Regulations 1999 require employers to assess risks — and if excessive heat is a foreseeable risk (which, in a UK summer, it increasingly is), it must be assessed and managed like any other workplace hazard.

When Heat Becomes a Health Risk

Heat stress occurs when the body can't cool itself effectively. Symptoms range from mild (discomfort, fatigue, reduced concentration) to severe (heat exhaustion, heat stroke, collapse). In extreme cases, heat stroke can be fatal.

The risk isn't just about air temperature. Humidity, radiant heat (from sun exposure, ovens, or industrial processes), air movement, workload intensity, clothing and PPE all affect how the body manages heat. A warehouse worker in PPE at 28°C may be at greater risk than an office worker at 32°C with a desk fan.

Groups at higher risk include pregnant workers, workers on certain medications, workers with pre-existing health conditions, and those performing heavy physical labour.

What Employers Should Do

When temperatures rise, employers should conduct a thermal comfort risk assessment. This isn't a complex document — it's a practical evaluation of how heat affects your workforce and what controls are available.

Practical measures include providing fans or portable air conditioning, ensuring access to cold drinking water, allowing flexible working hours (earlier starts, later finishes to avoid peak heat), relaxing dress codes where possible, rotating workers in hot environments to limit exposure, ensuring adequate rest breaks, providing shaded rest areas for outdoor workers, and monitoring workers for signs of heat stress.

For workers in inherently hot environments (kitchens, foundries, bakeries, laundries), heat management should be built into the normal risk assessment rather than treated as a seasonal issue.

The Productivity Argument

Beyond legal compliance, there's a straightforward productivity case. Research consistently shows that cognitive performance declines as temperatures rise above 25°C. Error rates increase, concentration decreases and decision-making deteriorates. In a warehouse or manufacturing environment, reduced concentration translates directly into increased accident risk.

Keeping people comfortable isn't just welfare — it's operational efficiency.

The Bottom Line

There's no magic number that tells you when it's too hot to work. But the absence of a maximum temperature doesn't mean employers have no obligations. If heat is affecting your workers' health, safety or welfare, you have a duty to assess the risk and take reasonable steps to manage it. The law is less about thermometers and more about whether you've done what a reasonable employer would do.

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York Green Safety Partners provides practical health and safety advice for businesses across the UK. Based in Cheshire, covering the whole country.