Motorists have already experienced delays as millions head off for a potentially sunny August Bank Holiday.
Seven million people are expected to travel by car over the weekend
Friday afternoon saw lengthy queues on some roads as many of the seven million people planning to travel by car set off early.
The weekend, which is not a bank holiday in Scotland, is also set to be busy for ports and airports - with about 1.7 million travelling abroad.
Forecasters say temperatures in parts of the UK should reach about 25C (77F).
The Highways Agency said roadworks have been suspended on a number of routes and traffic officers would be out on motorways near Birmingham and sections of the M25, M23 and M3 to deal with any incidents.
But traffic started to build up on Friday afternoon, with the M6 southbound between Warrington and Knutsford and the A303 westbound in Wiltshire around Stonehenge seeing some of the worst of the queues.
There were also early tailbacks on the M62 in West Yorkshire, with eight miles of queues eastbound from junction 27 at Gildersome to junction 24 at Huddersfield.
An estimated 400,000 passengers are expected to fly out of Heathrow on Friday and Saturday, with 250,000 passing through Gatwick airport and 150,000 through Stansted.
Another 400,000 travellers are expected to pass through regional airports, including Manchester and Nottingham East Midlands.
Eurostar is expecting to carry tens of thousands of passengers to the Continent, despite a strike for parts of Friday and Saturday by security guards at Waterloo and Ashford in Kent.
Managers said services on Friday had not been not affected by the action from about 130 members of the Rail Maritime and Transport Union in a row over pay.
The union warned that safety and security standards could be affected if untrained staff were brought in to cover for the workers, who are employed by Chubb.
But Eurostar said: "We would not be allowed to operate if there was any risk to staff or traveller security."
On the UK's mainline railways there will be engineering work on tracks in some areas, including essential work across the east of England, said Network Rail.
One of the biggest tasks was an £800,000 project between Clapton and Chingford, used by many passengers travelling to and from London's Liverpool Street station.
There will also be work between Gloucester West and Severn Tunnel Junction.
A Network Rail spokesman added: "Passengers will be pleased to learn that there will be no closures on mainline routes this August Bank Holiday Monday. Network Rail will be prioritising our engineering work on lightly used routes over this period."
According to BBC weather forecaster Peter Gibbs there is still some uncertainty about what the weather will hold for the Bank Holiday.
"But the signs are the southern parts of the UK will have quite a nice weekend," he said.
"Northern parts won't be fairing so well, experiencing some wet and windy weather in Scotland and Northern Ireland on Sunday, although Saturday should be reasonable everywhere.
"Then on Monday there is a chance of cloudy weather hanging around central parts of the UK."