Millions of families have to deal with misery on the holiday, because extra cars end up on the highways and the rain falls over a large part of the country.
The Met Office predicted sunny and cloudy weather for most parts on Saturday, but many of the UK are expected to experience "a good six hours" of rain showers on Sunday.
Predictors predict that the sunny weather will return on the public holiday on Monday, along with some clouds.
Sky News weather producer Chris England said: "It will be a rather cool bank holiday weekend, with a risk of a ground frost in the countryside on Saturday mornings and with temperatures usually below 20C, 68 Fahrenheit during the day.
"Saturday will be fine for manybut the Sunday will bring long-term and locally heavy rain from the West, although that will obviously be expected by the extreme east by night.
"Most places can expect a good six hours of rain.
"On Monday it will be mostly dry and a bit warmer than the weekend, but there will be showers.
"Northwestern parts are most at risk."
The RAC predicts that up to 14.4 million cars will be transported to the British major roads until Monday.
The breakdown insurer, which investigated the intentions of drivers with the ravel information provider INRIX, said that around 11.2 million people have planned car rides during that period.
Another 3.2 million say they will drive, but are not sure what day they will take.
Friday and Saturday are probably the busiest days for recreational & # 39; trips, because research shows that 3.6 million cars are expected to travel on both days.
INRIX data show that the M5 is hit most severely between J4 and J1, with travel times increasing from 21 minutes to 1 hour and 21 minutes.
It is predicted that the M1 will be hit hard from J22 to J25, with travel times increasing from a typical 16 minutes to 62 minutes on Saturday.
Highways England lifts and completes more than 300 miles of roadworks on freeways and major A-roads from Friday morning to help drivers more easily reach their destination.
RAC spokesman Rod Dennis said: "Although the holiday at the end of August is not typically one of the busiest on the road because it falls in the middle of the school holidays when people are already gone, in the UK or abroad, it still has a huge potential to put a block on the main roads, especially if we would see the sun make a welcome return.
"There are many well-known hotspots on the motorway network, but probably the largest in the summer months is the Almondsbury junction in Bristol, near the RAC building, where the M5 and M4 meet.
"While tens of thousands of drivers drive to Devon and Cornwall, traffic congestion leads to frequent traffic jams every Friday afternoon."
Rail passengers hoping to travel between London and major cities, including Manchester and Birmingham, will be hit by the closure of Euston station.
Virgin Trains stated that "due to extensive technical work on the west coast route" the station will not perform services between Saturday 25 and Monday 27 August.
The company adds: "We strongly advise you not to travel on these dates unless it is absolutely necessary."
Northern Rail's customers will also be affected, as the RMT trade union confirmed that a 24-hour strike would continue on Saturday.
The action is part of a continuing argument about the future of train guards.
Important events across the country that can be influenced by travel issues include Reading and Leeds music festivals, Notting Hill Carnival in London and the Rugby League Challenge Cup at Wembley Stadium.