Households in 38 UK areas are being told to switch off appliances, TVs and other electronics from 3pm until 11pm due to a yellow weather warning. The Met Office has issued a thunderstorm warning in England and Wales, with 38 areas in total told to take action to prepare for thunder, lightning and potential flash flooding.

Areas including London, Somerset, Cardiff, Hereford, Hampshire and Cornwall and Devon are among those at risk of thunderstorms from 3pm today, the Met Office warned. In its own advice, the forecaster said households should prepare for the storms by gathering items for power cuts, such as torches and batteries, a charged mobile phone and a flood kit.

Charity, The Red Cross, also has guidance available for households facing thunderstorms, and it recommends that appliances be switched off.

It says: “Yes, you should turn off and unplug any non-essential appliances during a thunderstorm to prevent them from being damaged by a power surge. That includes the internet or any plugged-in electrical devices.

“You’ll have to wait until the storm has passed before it’s safe to watch TV, but you can still use a tablet or laptop if they’re not plugged into the main power supply. You should also avoid using landline telephones that plug into the wall, but mobile telephones are safe.”

Not only that, but you shouldn’t stand at the window to watch the storm either.

The Red Cross adds: “ Many people enjoy watching a thunderstorm rolling over, but even inside your home, they still pose a risk. Lightning can travel through metal wires and bars, and concrete in walls and flooring, so don’t lean on exterior walls during the storm.

“If there are high winds, then there’s also the risk of large objects being blown into the building you are in, like trees. It's best to stay away from windows and doors just in case.”

The Met Office said in its warning: “Many areas missing the worst but thunderstorms this afternoon and evening likely leading to some disruption in places.

“After another hot day, thunderstorms are expected to develop across parts of Wales as well as some western and southwestern parts of England during this afternoon and through the evening. While many places will miss the worst conditions, where thunderstorms do occur they bring the potential for torrential downpours of rain, frequent lightning, large hail and strong, gusty winds.”

The full list of areas affected by the warning is: