The spring bank holiday getaway has begun, with travellers having to put up with the first bout of widespread unsettled weather for a while.
With the first of an estimated 15 million cars taking to the road, forecasters warned of cooler and showery weather, with possibly strong winds in Scotland and Northern Ireland on Sunday.
The weather was likely to put a dampener on the host of sporting events and music festivals taking place over what will be the last bank holiday for three months.
The biggest event is the Champions League football final at Wembley between Manchester United and Barcelona, a match that will bring travel congestion to north-west London on Saturday evening.
Twickenham in the south-west of the capital will also be busy as the ground is staging the Aviva Premiership Rugby final on Saturday.
Motoring groups predicted that the traffic build-up would begin around lunchtime on Friday, with Saturday also expected to be a busy day on the roads.
The AA said routes to south-west England and coastal resorts would be among the busiest.
Engineering work will affect a number of mainline train services over the weekend, but the Association of Train Operating Companies said 8% more trains would operate than during the spring bank holiday weekend last year.
Matt Dobson, of MeteoGroup, said the weather was expected to stay unsettled over the bank holiday weekend, with daytime temperatures as low as 9C (48F) in some parts.
He said: "We've had a very dry spring and it could be one of the warmest on record. But it's going to be cooler and rainier over the next few days, with showery rain across southern England in the middle of Saturday and high winds and frequent showers in some places in Scotland and northern England."