An amber heat warning has been issued for large parts of the UK, with Hertfordshire among the regions bracing for a heatwave that could see temperatures well into the 30s.

The UK Health Security Agency has issued the warning for all areas of England apart from the North East until 9pm on Sunday, with the hottest temperature of 2023 set to be recorded.

The mercury has been predicted to reach 32°C in Hertfordshire, with some spots in the south east likely to hit 33°C, according to the Met Office.

"High pressure is situated to the southeast of the UK, which is bringing more settled conditions and temperatures well above average for the time of year," said Met Office chief meteorologist Neil Armstrong.

"While the highest temperatures are expected in the south, heatwave conditions are likely across much of England and Wales especially, with parts of Scotland and Northern Ireland also likely to see some unseasonably high temperatures.  

"An active tropical cyclone season in the North Atlantic has helped to amplify the pattern across the North Atlantic, pushing the jet stream well to the north of the UK, allowing some very warm air to be drawn north.

"It’s a marked contrast to the much of meteorological summer, when the UK was on the northern side of the jet stream with cooler air and more unsettled weather."

The heightening to an amber alert means an increased risk to vulnerable people, including those aged over 65 with health conditions and young children.

And Met Office deputy chief meteorologist Steven Keates has also warned that the heatwave could break with thunderstorms next week, adding: "A cold front will begin to influence things from the northwest towards the weekend, though it’ll remain very warm or hot in the south.  

"There’s a chance the thunderstorm risk to western areas from Friday onwards may require a warning response, with some potentially impactful downpours, though exact details on the likely positioning of these downpours are still being determined."