The hot spell in parts of Britain is set to build to a "crescendo" on Friday as temperatures soar to a sweltering 34C in some parts.
Ahead of the weekend, conditions will heat up on Thursday with predicted highs of 29C in London and the surrounding area.
The mercury is then expected to soar on Friday to a possible sizzling 34C in the the South East- with temperatures between 27C and 30C across most of England and Wales.
The warm blast from Spain and Portugal could see temperatures rocket so high they could set a record for the hottest day in June since records began.
The highest recorded June UK temperature was 35.6C at Southampton Mayflower Park in June 1976 - the year of a notorious summer heatwave.
This year's hottest day so far was the 27.5C set in mid-May at Heathrow.
Met Offic e spokesman Grahame Madge said: "We have got high pressure at the moment so we are getting a certain amount of natural home-grown heat building up because obviously we have got clear skies and fairly dry ground conditions across southern England.
"We have also got warmer air being brought up from further south in Europe where there has been a major heat incident, particularly in Iberia, so that's leading to the sort of crescendo we will see on Friday.
"Because of the direction of the flow, with the weather pattern we have got set up in our latitude, that is encouraging this warm flow of air to come further north.
However, on the back of scorching sun, the Met Office said there's a chance it could be followed by rain and even thundery showers.
Grahame added: "The next couple of days will be hotter than the preceding day. We think at the moment, although there is some uncertainty, that the weather temperatures will peak on Friday and then largely we will be in for a cooler day on Saturday.
"Heat may remain potentially into Saturday but for most parts of the UK, because we have got a cold front moving down from further north, we will see temperatures coming back down - but they may just hang on in southern England."
Dr Mark McCarthy, head of the Met Office's National Climate Information Centre, said: "Climate change has increased the average temperature of UK summers, and it is also increasing the likelihood of experiencing more extreme temperatures during hot spells and heatwaves.
"Reaching 34C during June is a rare, but not unprecedented, event in the historical climate records for the UK. But if it should happen this week it would be notable that it would have occurred on three days during the last six Junes."
The previous year such temperatures were reached in June was 1976. First aid and health response charity St John Ambulance has issued some tips on coping with the hot weather.
Its medical director, Dr Lynn Thomas, said: "If you're out and about in the sunshine, it's important to make sure you look after yourself by staying hydrated, keeping out of the sun at peak times, and by wearing sunscreen with a minimum SPF30.
"I would also encourage anyone with elderly relatives and neighbours to check in with them, as any increase in temperature can be dangerous."
RAC spokesman Rod Dennis said: "With the temperature ramping up very rapidly this week, we're expecting a short, sharp spike in breakdowns, especially in central and southern parts of the UK.
"It's important drivers don't get caught out, so we're advising they check their car's oil and coolant levels as soon as they possibly can, particularly if they have a long trip planned in the hottest part of the day.
"Drivers should also stay hydrated, which has been shown to have a positive effect on their concentration levels.
"Passengers should also be kept as cool and comfortable as possible, so carry plenty of water and plan in sufficient breaks to avoid an already hot car becoming even more heated."
