Drivers have been urged to remove hand sanitiser from their cars during the heatwave as it could set their vehicle on fire.
Surrey Fire and Rescue said alcohol-based gels may become heated when temperatures rise over the next few days and result in “flammable vapours being released”.
The fire service posted a picture of a melted car on Facebook with the message: “Please do not leave hand sanitisers in cars during this hot weather.
“Alcohol-based hand sanitiser can become heated, resulting in flammable vapours being released.
“Help us prevent these vehicle fires and enjoy this lovely weather safely.”
Wednesday could be the hottest day of the year, with temperatures expected to hit 30C in London, which would beat the 28.2C set in Suffolk on 20 May, the Met Office said.
Drivers have been keeping more sanitiser in their cars after the public were advised by health experts to clean their hands regularly to stop the spread of coronavirus.
The NHS has also warned its staff to remove hand sanitisers from their vehicles because of a potential fire risk.
It posted pictures of melted cars, adding: “We have received a number of reports of hand sanitiser being the cause of fires when left in vehicles in the hot weather the UK is currently experiencing.
The notice said: “These vapours are reaching their ‘flashpoint’ and then ignite in normal air conditions, setting fire to flammable components within the car.
“Remove all alcohol-based hand sanitiser products from vehicles when they are not occupied, do not leave hand sanitiser in unattended vehicles.”
London Fire Brigade has warned people not to have barbecues on dry grass, not to drop cigarettes or matches, and not to leave rubbish such as glass bottles lying around amid a risk they could start fires.
Deputy commissioner Richard Mills said: “Barbecuing on dry grass is thoughtless and reckless and can easily be the cause of a significant fire, which isn’t something you want on your conscience.”
Warnings have been issued about UV levels, which are going to be “exceptionally high” over the next couple of days.
Shoppers have also been advised to be aware they could be forced to spend extra time in the sun as a result of social distancing measures.
The public are also being reminded to take care around water throughout the summer, amid concerns people might be tempted to take a dip to cool down.
Emergency services rushed to the River Thames in Cookham, Berkshire, on Tuesday evening after reports that a man was missing after going into the water.
Beaches were busy as people took advantage of the good weather after months of lockdown spent at home.