The Bank Holiday getaway begins tonight with warnings that roads will be packed and many trains replaced by buses. Jams and delays are as traditional a part of the August Bank Holiday as scattered showers, and tonight will be the worst time for heavy traffic, the RAC said.

Music festivals around the country are likely to cause disruption while roadworks remain in place on the northern M25, parts of the M4 and the A46 in the West Midlands. And with 42 sets of engineering works on the railways, buses will replace trains on an estimated 1,000 miles of track.

Travel operators are reporting a late surge in foreign holiday bookings as the British weather dampens the appeal of staying at home. An estimated 1.9 million Britons will travel abroad over the Bank Holiday, according to the travel agents’ association Abta.

“Many families see the Bank Holiday as their last-ditch attempt to get a holiday abroad for some guaranteed sunshine,” said John McEwan, the Abta chairman. “This is more true this year than ever.

“Obviously people have been holding on to their money until they are sure they have enough to go away with and, as a result, we have seen a surge in late bookings.”

Those who remain in the South East of England are likely to get a warm and sunny weekend, according to the Met Office, with temperatures predicted to reach 25C (77F) to 28C on Monday. “Monday is the day to pack your bucket and spade and head for the coast,” said Barry Gromett, a Met Office forecaster.

However, other parts of the country will have showers tomorrow, which could last throughout the long weekend. “The further north and west you go, the more likely you are to see cloud and rain,” Mr Gromett said.

The AA said that this weekend there would be some of the busiest traffic of the year, which is likely to be worst in Yorkshire and Humberside. The RAC said that traffic hotspots are likely to include the M6 in the Lake District, the M55 towards Blackpool, the M5 southbound through the West Country and the A303 around Stonehenge in Wiltshire.

The Reading Festival is likely to add to congestion in Berkshire, and there are also music festivals in Leeds, Glasgow, Cheshire and Cumbria. The Notting Hill Carnival will be in full swing in West London on Sunday and Monday. The Rugby League Challenge Cup final is at Wembley on Sunday.

On the railways, buses will replace trains on 1,000 miles of track, according to the Liberal Democrats, who have called for rebates for rail passengers who have to travel by replacement bus.

“Spending hours in a hot bus is not the way most of us want to spend our bank holiday but with miles of rail replacement buses planned yet again, it’s going to be hard to avoid,” said Norman Baker, the party’s transport spokesman.

“Passengers who have paid for a rail journey have the right to expect to travel by train. Companies that force passengers to travel part of the journey by bus should give them a substantial rebate on the cost of their ticket.”

But the Association of Train Operating Companies said that 3,500 more trains are running than during the August Bank Holiday last year, and there are 15 per cent fewer replacement bus services than last year.

Times recommends

• 'New York has lost its edge'
• The UK and Ireland's 25 best Christmas events
• Chalet Chef 2010: the winners