Traffic is set to peak at 28 per cent above typical levels at 5pm on Thursday as motorists embark on the bank holiday getaway, according to transport information supplier Inrix.
It said the worst affected roads will be major motorways, with some journeys taking as much as three times longer than normal.
Inrix said the worst times to travel will be: Thursday between 4pm and 6pm; Friday between 10am and 2pm; and Monday between 12pm and 5pm.
Easter Sunday is expected to be the quietest day on the roads with 25 per cent fewer vehicles than an average Sunday.
A number of rail services will be disrupted as Network Rail carries out more than 200 engineering projects.
Trains to Edinburgh, Glasgow, London, Manchester and Bath are among those affected.
Network Rail said it is doing the work over the four-day weekend as fewer passengers use the railways on bank holidays.
Airports are also expecting a rush of holidaymakers jetting off overseas. Some 868,000 people are due to travel through Heathrow Airport alone between Good Friday and Easter Monday, including an extra 200,000 families compared with a typical Friday to Monday period.
Inrix head of research Graham Cookson said: “With UK drivers spending an average of 30 hours in congestion last year, motorists are no stranger to sitting in traffic.
“We expect significant delays over the Easter period due to a combination of factors, including the regular post-work peak, the start of the school break, people travelling on holiday, railway engineering works and Tube closures. Our advice to drivers is to consider alternative routes or avoid peak times.”
The warning to motorists came as the UK enjoyed the hottest day of the year so far. Sunseekers flocked to the beaches and parks as the temperature topped 25C (77F) in Cambridge, and rose to at least 20C (68F) in many parts of England and Wales.
However, as much of England and Wales enjoyed warm weather all weekend, conditions cooled yesterday in Scotland, with highs of 16C (61F). And temperatures in some parts of the UK are expected to drop by as much as 10C today as the weather returns to normal for this time of year.
Met Office forecaster Emma Boorman said it was too early to give an accurate forecast for Easter but the weather is not expected to reach the sunny highs of yesterday and Saturday.