Roads are expected to be busy and ferry passengers have been warned of queues at Dover as people head away for the bank holiday weekend.
Drivers across the UK are expected to make 19.2 million leisure car trips between Friday and Monday, according to estimates from the RAC, with the hottest day of the year so far forecast on Sunday.
Journeys on some stretches of the M25 could take up to three times longer than normal, transport data company Inrix has warned.
Long delays are also expected on the M5 in Somerset and the M6 in Cheshire and Greater Manchester.
Ferry passengers through Dover are being advised to allow two hours to complete border controls and check-in.
DFDS ferry company tweeted: "Please be prepared with refreshments & use facilities before arriving at the port."
The Port of Dover said delays at French border control were due to "IT issues" with "high volumes of tourist and freight traffic on Port approaches".
A traveller in the queue at Dover told Sky News they believed the "sticking point was French frontier control".
"Once we got past that, inside Dover moved really well," they added.
The RAC said it was expecting the busiest weekend of traffic since before the pandemic.
"Getting away early in the morning or delaying trips until the evening are the best way to avoid the inevitable delays," spokesman Rod Dennis said.
While holidaymakers face the prospect of long queues, those staying at home for the long weekend should enjoy some of the hottest weather of the year.
Southeast Wales and around the Bristol Channel will get the best of the weather, with temperatures up to 24C on Saturday and Sunday.
Other parts of the UK could see temperatures reaching the high teens and low 20s.
The dry and bright weather is likely to continue for most with little rain expected throughout next week during half term.