UK weather: Britain set to be hotter than Istanbul but warm weather sparks warnings for thunderstorms

Forecasters warned of intense thunderstorms developing because of the warm airmass on Saturday

Sunbathers enjoy the warm weather on Southsea beach, Portsmouth, on May 7, 2016. (PA)

Parts of the UK are set to be hotter than Istanbul on Sunday, with forecasters predicting the hottest day of the year so far.

South-east England is due to see the hottest temperatures of up to 26C, compared to a cooler 22C in Turkey’s largest city and just 16C in Barcelona.

But the warm air mass bringing the summery conditions to the UK sparked severe weather warnings for possible thunderstorms.

The Met Office issued a yellow warning for rain in southern England, the Midlands, Yorkshire, North West and Wales, which was in effect until 10pm.

Its chief forecaster said there was a risk of “isolated intense thunderstorms” developing, bringing downpours, lightning, hail, strong winds, travel disruption and potential flooding.

“The atmospheric conditions are there for frequent lightning, torrential downpours, large hail of up to 20mm and gusty winds,” a statement said.

The threat of rain came as sun-seekers poured into British parks and gardens, making most of the fine and dry weather enjoyed by much of the country.

The thunderstorms were expected to pass over through the night, with cloud clearing to leave a hot and sunny day.

Emma Boorman, a spokesperson for the Met Office, said: “Sunday is looking like it is going to be the peak of the warmth.

"It is not the same everywhere though – much cooler, cloudier and with some outbreaks of rain further north and west, particularly Northern Ireland and western Scotland.

"Misty and murky conditions along the north-east coast of both England and Scotland will suppress the temperatures back in to the low to mid-teens."

London is predicted to hit 26C on Sunday, with Manchester at 24C, 23C in Birmingham, 21C in Cardiff and 20C in Glasgow.

People enjoy the sun in Potters Fields in London, as many parts of the UK enjoy a day of warm weather (PA)

Public Health England is urging people to protect themselves from sunburn as high UV ratings are expected.

"Sunburn and even a tan is a sign of overexposure to UV – that’s physical damage to your skin caused by UV,” a spokesperson warned.

"Sometimes people get burnt when it clouds over because they assume clouds protect them – they don’t.”

Anyone spending time outside is advised to wear a shirt, hat and suncream.

Additional reporting by PA