There is no legal maximum temperature for workplaces however, a statement from the HSE emphasised heat is classed as a hazard and should be included in risk assessments.
The warning came as the UK Health Security Agency and the Met Office issued a yellow heat-health alert for June 9 to June 12.
HSE said this alert – and the record high temperatures seen in Great Britain last summer – should prompt employers to take action to protect those working both inside and outside.
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Measures to cope with the heat include using blinds using blinds or reflective film on workplace windows to shade workers from the sun, placing workstations away from direct sunlight and heat sources and putting insulation around hot pipes and machinery.
The HSE also suggested offering flexible working patterns so workers can work at cooler times of the day, providing free access to drinking water and relaxing dress codes if possible.
It recommended weather-appropriate personal protective equipment where needed, and sharing information about the symptoms of heat stress and what to do if someone is affected.
HSE saw a surge in people seeking advice last summer, with visits to its online hot weather working guidance increasing by nearly 1000%.
The number of concerns relating to hot weather reported to HSE almost doubled in July 2022, when temperatures exceeded 40°C.
John Rowe, head of operational strategy at the HSE said last summer should have been a wakeup call for employers.
He said: “Climate change means we’re likely to get hotter summers and that could have a big impact on the workforce of this country, affecting everything from the health of workers to productivity on construction sites.
“We know all employers are under pressure and we don’t want to add to their burden but it’s vital they think hard now about simple and cheap measures they can put in place to support workers should we see extreme heat again this summer.”