Britain's heatwave is only expected to last for the start of the Easter holiday break.
Thousands headed for the beach to enjoy the unseasonal heat
Sunseekers will be disappointed at the weekend, when temperatures are expected to plummet as the weather worsens.
UK temperatures on Wednesday matched those of Cyprus and beat those of Greece, Italy and coastal Spain, where many Britons are heading over the Easter break.
Despite the heat, 1.8 million people are expected to leave Britain, with a million passengers departing by air.
And if last year's figures are repeated, 2.6 million Britons are set to holiday in the UK and spend an estimated £400m.
But their rail journeys are likely to be disrupted by industrial action from train guards, affecting on average one in five services.
The AA expects 18 million motorists to take to the roads over the holiday period, with traffic peaking from mid-afternoon on Thursday to
the end of Good Friday.
But the sunshine will not last throughout the holiday weekend.
Michael Fish, broadcast meteorologist at the BBC Weather Centre, said: "It will stay sunny and warm everywhere on Thursday, except on the east coast.
"Temperatures will not be as high as Wednesday, with a maximum of 24C in the west.
"Friday will be fine and sunny, but not as warm, and Saturday will be much colder, with rain by the end of the day."
The weather is set to worsen on Sunday, with rain and thunderstorms spreading to Scotland on Monday.
But the travel industry is not complaining.
Stephen Bath, President of the Association of British Travel Agents, said:
"The travel industry has gone through a very difficult period in the last few
"However, I am delighted to see that holidaymakers have not allowed the
current situation to put them off taking a well-earned break this Easter and are
travelling in greater numbers than ever."
A total of 50,000 are departing from Luton Airport, 120,000 from Manchester, 38,000
from Birmingham and 30,000 from East Midlands Airport.
And more than half a million are expected to make Channel crossings including 60,000 on the London to Paris Eurostar train service.
For those staying in the UK, the Highways Agency has promised to keep roadworks on England's motorways and
trunk roads to a minimum over the holiday.
As a result of the unusually hot weather, scientists from the Department of the Environment, Food and Rural Affairs (Defra) say people with breathing disorders may suffer from high levels of ozone over the next couple of days.
Ozone is produced when sunlight reacts with polluting gases created mainly by vehicle exhausts.
The high levels in London and the South East are expected to last until Friday evening.