"Slow moving heavy showers will affect parts of Northern Ireland on Saturday morning, easing later on Saturday afternoon", the spokesperson said.
Temperatures are forecast to be in the mid-30s for much of east and south east England, reaching 37C in London, and could rise higher still if there is a lot of sunshine, Met Office meteorologist Alex Deakin said.
The Met Office has issued a Heat-Health Watch warning ahead of the scorching hot temperatures, which will see temperatures averaging 30C on weekdays.
There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds.
"Where these occur, expect torrential downpours with a much as 30mm of rainfall in one hour and 60mm in three hours".
Several places have had 54 consecutive dry days since 30 May including a few that have had less than 1mm of rain in the entire 54-day period - the longest spell since 1969, when 70 days passed with no significant rainfall, according to the Met Office.
Teen killed, sister wounded in train station stabbing attack
Video surveillance indicates that Cowell allegedly entered the parking structure at the station and discarded his clothes. BART Police says it has ramped up patrols and working video cameras have been placed throughout stations and on the cars.
Meanwhile sun worshippers in the United Kingdom have sizzled in the hottest temperature of the year so far, with a scorching 33.3C recorded in England yesterday. The risk of more significant thunderstorms increases later in the afternoon for Lincolnshire in particular, locally torrential with hail and briefly gusty winds.
He went on: "Weather fronts are trying to come in from the Atlantic and eventually they will do so".
"Lots of people heading out and away for the weekend, roads lie the M11, the A1, the M1, the M18 - a lot of surface water and spray on those roads, so allow some extra time for your journey".
The maximum temperature in the day will be 34 °C.
Meanwhile, London's fire chief has called for barbecue bans to be imposed in the capital's parks after a record-breaking number of grass fires.
But, the threat of rain also promises to send temperatures tumbling - with Saturday potentially being more than ten degrees cooler than the end of the working week.