The UK Health Security Agency (UKHSA) has issued a warning that using electric fans becomes dangerous when indoor temperatures hit 35°C or above. This advisory comes as the UK experiences its third heatwave of 2026, with amber and yellow heat health alerts in place across England and temperatures potentially reaching 36°C in some areas.
Why Fans Become Hazardous at 35°C
According to UKHSA guidance, mechanical electric fans can actually be harmful once the indoor temperature reaches 35°C, which is close to the human body's normal temperature. At this point, fans simply blow hot air over the body, rapidly drying out the skin and increasing fluid loss, which can lead to dehydration. The agency stresses that while fans are a common go-to for staying cool, they should not be used when the air temperature is 35°C or higher.
UKHSA's 'Beat the Heat' Campaign
The UKHSA launched the 'Beat the Heat' campaign to provide advice for everyone during hot weather. The campaign includes a list of recommended tips to keep cool without relying on fans when temperatures are extreme. Key suggestions include: closing blinds and curtains on windows exposed to direct sunlight during the day; closing external shutters or shades if available; moving to a cooler part of the house, especially for sleeping; opening windows when the air feels cooler outside than inside, such as at night, and trying to get air flowing through the home; using electric fans only if the air temperature is below 35°C, and not aiming the fan directly at the body as this can lead to dehydration; checking that any heating is turned off; turning off lights and electrical equipment not in use; and going outside if it is cooler outside in the shade.
Heatwave Conditions Across England
The warning comes as the UK faces its third heatwave of 2026, with the mercury expected to rise to 36°C in some parts of the country. The UKHSA has issued amber and yellow heat health alerts, urging people to take precautions to stay safe and well. The agency's guidance aims to reduce the risk of heat-related illnesses such as heat exhaustion and heatstroke.
