The Met Office has reported a high of 24.2C (75.5F) at Herstmonceux in East Sussex, the warmest early May Day bank holiday in 40 years.
The Met Office May-July forecast said above-average temperatures are favoured over the next three months.
The weather in the county is expected to cool down further later this week, with highs of 14C (57.2F) and lows of 5C (41F) on Friday.
The brief spell of summer weather is due to hot air coming in from 86F (30C) southern Russian Federation, leading meteorologists to dub the heatwave the "Roast from Russia".
Charlie Powell from the Met Office told Metro: "We're looking at top temperatures of 27-28C, possibly 29C in and around London, but well above average for the time of the year".
On the first official May Bank Holiday in 1999 the thermometer peaked at 23.6C, and before that, in 1995, we hit 28.6C, - with it touch and go whether we will sizzle above that.
In other parts of England yesterday, temperatures were expected to soar to 28C (82.4F).
Real Madrid see off Bayern to reach third straight Champions League final
On the possibility of his players looking to avoid injury ahead of the Liverpool clash, Zidane added: "We can't think about that. Heynckes said he expected a competent performance from the Turkish official.
Trump tries to sink Blankenship in West Virginia primary
In North Carolina, Democrats are eyeing two GOP-held seats they believe could be in play come November. Now he is trying to redeem himself - if that is the right word - by running for the Senate.
Chelsea keep top four hopes alive with crucial win over Liverpool
The Premier League outing between Chelsea and Liverpool will start at 4:30 pm local and 9 pm IST. We need to win to keep the pressure on both Spurs and Liverpool .
By 11am this morning we had already beaten the hottest early May Bank Holiday Monday record, since records began from it's inception in 1978.
"The first, for hottest spring Bank Holiday Monday, is nearly a dead cert now!"
The weather is set to become mixed as the month progresses, and the May 19 wedding of Prince Harry and Meghan Markle draws near.
He said: 'It looks like we should be prepared for some pretty changeable weather throughout the second half of May. PA Wire/PA Images People look at cherry trees in blossom as they enjoy the warm and sunny weather in Greenwich Park, south London.
The Met Office forecaster Greg Dewhurst said: "We have smashed the warmest bank holiday Monday for early May".
The weekend's hot conditions were created by a mix of low pressure, light winds and consistent sunshine.
He said temperatures will generally be above normal, but this will depend on whether it is a sunny day or a sunny wetter day.