Drivers have been warned that journeys could take three times longer over Easter as parts of Wales are expected to be hotter than the Mediterranean.
Good Friday is expected to be the busiest day on the roads as 27 million cars will clog UK roads over Easter.
The M4 around Newport on Easter Sunday is expected to be the busiest stretch of road in Wales and train lines into the country are to shut.
Meanwhile, Aberystwyth and Carmarthen are set to be Wales' hottest towns.
Forecasts predict they will reach highs of 22C on Good Friday - which will be hotter than Mediterranean resorts like Magaluf, Benidorm and the French Riviera.
Wales is also expected to sizzle on Saturday as temperatures in Cardiff and Wrexham are forecast to hit 21C.
BBC weather presenter Behnaz Akhgar said the warm weather would be almost double the April average of 12C.
"It's thanks to a combination of warm air from the south and high pressure that is expected to give us some lovely weather this Easter," she said.
"So get your sun hats and sun block ready but be aware that the pollen count will be high."
'Set off early'
Traffic experts predict the M4 motorway between the Severn Crossing and Cardiff will be busiest road in Wales - peaking at 17:15 BST on Sunday.
This could affect football fans heading to or from Sunday afternoon's Premier League game between Cardiff City and leaders Liverpool at Cardiff City Stadium.
The RAC has also warned stretches of motorway just outside of Wales will be among the UK's busiest this Easter - the M5 south at Bristol and the M6 in Cheshire.
"We are predicting Good Friday will be the worst for traffic from late morning into the afternoon," said Dan Croft, of traffic data analysts INRIX.
"For drivers looking to avoid the worst congestion, the best options are to travel on Saturday and set off early in the morning."
The Welsh Government has told all contractors to suspend road works in Wales over the long weekend "barring any emergency repairs".
Trains between Wales and London, Birmingham and the south coast of England will be affected by Easter weekend engineering works.
Buses will replace trains between Newport and Bristol - as the Severn Tunnel will close - and Newport and Gloucester, between Friday and Monday.
Travellers to and from north Wales and London have also been warned Euston - the London terminus for the Holyhead service - will shut over Easter.
More than 60,000 passengers are expected to fly in and out of Cardiff airport over the school holiday - a 15% rise on 2018 - with Amsterdam, Doha and Venice the most popular destinations.