Five regions of the UK have been hit with an amber weather warning this weekend as thunderstorms are expected to mar glorious 30C sunshine.
The UK Health Security Agency (UKHSA) increased its heat alert from yellow to amber in the West Midlands, East Midlands, East of England, South East, and South West.
Amber alerts are imposed when temperatures are deemed to potentially have an impact on people of all ages, which could put a strain on the NHS.
The alerts, which came into effect on Friday morning, will remain in place until 9am on Monday.
In a statement, the UKHSA said: "The decision to move to an amber alert has been made due to latest Met Office forecasts, which indicate there is a high likelihood that forecasted temperatures will be reached rapidly over the weekend in these regions, while we are also likely to see high overnight temperatures."
The Met Office says the warmest period - the peak of the heatwave - will be at around 2pm to 3pm on Saturday.
The South East of England, including London, will be the hottest region during this period.
Jim Dale, meteorologist for British Weather Services, said: "This is definitely going to be the hottest weekend of the year so far.
"We could see 30C in parts of the country, or even 32C as an outlier as warm air comes in across Europe and France from Africa, and into the UK. For much of the country, we are looking at highs of 28C or 29C on Saturday."
As the temperatures soar, meanwhile, predicted thunderstorms have brought about their own associated warnings.
The Met Office says warm air from the south will bring thundery showers with it - and potentially gusty winds and hailstorms.
Chief meteorologist Frank Saunders said temperatures could reach 31C in parts of central and south east England on Saturday – and with it the chance of torrential rain.
"As the heat builds from the south, thundery showers will develop through Saturday afternoon," he said. "While not everyone in the warning area will see the heaviest showers, or even any rain at all, some will bring heavy thundery downpours.
"With intense showers there is a risk of surface water flooding which could cause some disruption."
A yellow thunderstorm warning – signalling the potential disruption of travel, power cuts and localised flooding – is in place in Wales and large parts of southern and central England from 2pm to 9pm on Saturday.
A second warning has been issued for Sunday running from 12pm to 9pm in Wales, Northern Ireland and the majority of western and central England and Scotland.
Mr Saunders added: "Sunday will see 30C again in parts of southern UK and the risk of thunderstorms more widely – particularly western and central areas."
The Met Office adds the thundery showers could continue well into Monday, with hot and humid conditions expected until the middle of next week.
UK weather forecast
Today:
Morning cloud slowly clearing, then plenty of sunny spells. Turning increasingly hot and humid, giving way to thundery showers by the afternoon. Some localised flooding is possible.
Tonight:
Showers mostly dying out in the south, but continuing overnight in the north. Cloudy and murky around some coasts. Warm and humid.
Sunday:
Staying hot and humid for many through this period, with plenty of sunny spells. The continued risk of some heavy and thundery showers developing. Warm and humid nights.
