by Heavy showers and thunderstorms are due to hit parts of the UK over the weekend, according to the Met Office, after a heat-health alert was issued.
The alert, due to last until Sunday, covers six English regions and warns of increased health risks – with temperatures set to hit 30C (86F).
But the Met Office has now said that following those highs, thunderstorms can be expected throughout Saturday.
At-risk regions for rain span the Scottish Highlands down to London.
The UK government’s Health Security Agency and the Met Office issued a yellow heat-health alert on Thursday for six regions in England: London, the South East, East Midlands, West Midlands, East of England, and Yorkshire and the Humber.
The alert lasts from midday on Friday until 09:00 BST on Sunday.
A Met Office yellow warning for thunderstorms means there is a small chance homes and businesses could be flooded quickly and communities cut off by floodwater, while spray and sudden flooding could cause difficult driving conditions.
A brief but potent burst of heat and humidity will see temperatures at their highest on Friday in East Anglia and south-east England, with 28-30C possible, according to BBC Weather’s Matt Taylor.
On Saturday, northern Scotland and eastern England will experience temperatures into the upper 20s. And the night will be particularly muggy for many.
But that will be short-lived, the forecaster added, with thunderstorms on Saturday expected to break out widely across the UK. For some, these could be severe with intense rainfall, hail and gusty winds.
Norwich, in eastern England, Manchester in the north-west and Scotland’s capital Edinburgh all fall within the Met Office’s yellow weather alert for thunderstorms.
The alert warned of a number of scenarios, including the flooding of homes and businesses and the cancellation of public transport in affected areas.
It covers half of Northern Ireland on Friday, from 11:00 to 18:00, and a majority of England and Scotland the following day, from 09:00 to 23:59. Wales sits mostly outside the predicted at-risk boundary line.
One area forecast to be hit by the storms on Saturday is Wimbledon, south-west London, where the annual Grand Slam tennis tournament is currently taking place.
On Tuesday, rain caused the worst disruption to the Championships for years, with dozens of matches suspended.
Organisers were forced to issue a huge number of ticket refunds as a result – and reports suggest this cost them hundreds of thousands of pounds.
