Drivers have been warned to expect major traffic jams as millions of people take to the roads this weekend for the beginning of the summer getaway.
An estimated 3.8 million leisure trips are to take place by car between Friday and Saturday, the RAC said.
The M40, M5 and the A303 in the south and south west are expected to be the worst hit by delays on what has been called “frantic Friday”.
The AA urged drivers to carry out maintenance checks on their vehicles and take basic supplies, with high temperatures putting extra strain on cooling systems and tyres.
The organisation's president, Edmund King, said: "If your car breaks down your air conditioning might not work either, so make sure you have plenty of drinking water in the car, especially if you have young or elderly family members with you."
Transport data firm Inrix warned that some routes, particularly those popular with holidaymakers, will experience lengthy delays compared with a normal Friday.
Those heading south on the M5 between Gloucester and Devon should expect hold-ups of about an hour and a quarter, while westbound journeys on the A303 between the M3 in Hampshire and A37 in Somerset could take an extra hour.
Some 2.5 million British holidaymakers will head overseas this weekend with Mediterranean hotspots proving popular, travel trade organisation Abta reported.
Spain is the most in demand location while bookings are up for trips to Turkey, Egypt, Greece, Bulgaria and Croatia.
Airports in the South East are expecting a busy weekend with over half a million passengers departing from Heathrow, 250,000 from Gatwick, 148,000 from Stansted and 88,000 from Luton.
Elsewhere, there will be 160,000 people flying from Manchester and 67,500 from Birmingham.
