Britain could become a nation of beach bums with millions set to skip work for the seaside to bask in 31C temperatures – making it hotter than Hawaii.
A 1,500 mile-wide 'Saharan spurt' of hot air which has settled over the UK promises to deliver the most sweltering September 15 in nearly 200 years.
The Met Office predicts temperatures will soar 11C above the 20C average putting 29C Pukalani in Maui, Hawaii, in the shade.
Sea temperatures off the south coast will rocket to a 'tropical' 19C – making the water warmer than in Brazil.
It is even expected to hit 26C in the north.
Experts predict up to 70% of Brits will be tempted to skip work to soak up the sun – at a cost to their employers of £500million.
Due to the pandemic many are already working from home – away from the prying eyes of their bosses.
That makes them even more likely to bunk off to the beach.
Sick days cost employers an average of £139m per working day covering for absent staff.
According to the Chartered Institute of Personnel and Development 70% are tempted to throw a sickie during a heatwave.
The Federation of Small Businesses has said: "Employees’ days off in hot weather do happen and can be a big problem.''
Experts fear 'Toasty Tuesday' may have a bigger impact as locked down workers take the opportunity to escape isolation.
If – as expected – today's temperature beats 30.6C recorded in Suffolk in 2016 it will be the hottest September 15 since records began in 1841.
And forecasters predict the awesome autumn will continue.
It is expected to be 27C tomorrow then 24C into the weekend and remaining warmer than normal from September to November.
The Weather Outlook forecaster Brian Gaze said: " Autumn's heat wouldn't be out of place in midsummer.
"Saharan air is bringing Indian Summer-style conditions.''
Ex-BBC and Met Office forecaster John Hammond, of weathertrending, said: "September is putting on a show - so fill your boots.
"Blue skies should prevail for much of the week.''
Met Office forecaster Marco Petagna said: "31C is expected. The jet stream is dragging heat into the UK.''
While fellow forecaster Bonnie Diamond said: "Tropical continental air is pushing up.''
The Met Office's autumn forecast, being briefed to councils and businesses, said: "September-November has above-average temperatures more likely than below-average.''