The UK Health and Safety Agency and the Met Office have put a heat health warning in place across most of England until 9am on Monday.

The warning covers the South East, South West, East Midlands, West Midlands, East of England, Yorkshire and the Humber, and London.

London is expected to be the hottest part of the UK with potential highs of 31C or 32C, but temperatures will be in the high 20s for large parts of England.

Check the five-day forecast for where you live

Met Office forecaster Marco Petagna said: "Tomorrow (Saturday) we're looking at a North West/South East split across the UK, with Scotland and possibly Northern Ireland seeing some showering bits of rain, but particularly toward the north and west of Scotland by the looks of things.

"A little bit breezy in the North West there as well but despite that, even with the cloud there, it's going to be a warm day.

"Certainly, the warmest conditions will be developing across England and Wales, and especially towards the South East, with plenty of sunshine developing after a bit of a grey start.

"There's a possibility of a bit of drizzle across western hills, but much of the UK away from the west will be very warm if not hot sunshine during the day.

"As we head into the afternoon we're looking at highs in the north touching 24C or 25C, and in the South East many places getting into the high 20s. London could see 29C, maybe even 30C."

Mr Petagna said there will be split conditions on Sunday as band of showery rains move in from the West and could turn "quite rainy and thundery", particularly across northwestern areas.

Met Office Chief Meteorologist Matthew Lehnert said: "There are some marked contrasts in the UK's weather this weekend, with some potentially impactful thunderstorms developing affecting the northern half of the UK on Sunday, while further south it will become hot.

"For those in the North, there is a chance of thunderstorms developing as we see a change to cooler conditions with a chance that these could become organised with heavy rain, hail, lightning and gusty winds.

"Whether thunderstorms develop is finely balanced and there is a possibility of warnings being issued, so keep an eye on the forecast this weekend for any updates."

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The Met Office has said it will be a "very hot day" in the southeast of England where temperatures could reach as high as 31 or 32C.

The hottest day of the year so far fell on 10 June when 32.2C was recorded in Surrey.

Mr Lehnert continued: "Official heatwave criteria could be met for parts of southern and eastern England by the end of the weekend. It's worth noting the temperatures in the south will remain quite high overnight this weekend, so it's important to look out for those who may be more vulnerable to heat."

Heatwave criteria is met when a location records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold.

The map below shows how the heatwave threshold varies by UK county.

Thousands who are descending on Somerset for Glastonbury will welcome the warm weather, although they could see some rain and thunder moving in from the West.

Mr Petagna said: "For those headed to the festival, tomorrow looks like another fine day, plenty of sunshine there.

"There will be an increased chance on Sunday, from that weather front I mentioned from the west, of a little bit of rain developing across Glastonbury.

"You need to keep an eye on that as it could be very sharp.

"Very warm throughout, temperatures in the mid 20s, 25C or 26C and the fresher air coming in for when things are finishing up on Monday."