Heavy rain and wind will roll in across southern Britain tomorrow, spoiling the last long weekend of the year, weather experts have warned.
The Met Office has issued a sweeping yellow weather alert for Bank Holiday Monday, predicting travel problems for the millions of people returning home from a weekend break as surface water builds up on the roads.
Meanwhile, overnight temperatures will plummet to freezing point in some areas, with the first frost of the summer arriving in the north this morning.
Despite a cold start, today will be largely fine across the UK with spells of sunshine and highs of 18C (64.4F).
Tomorrow's weather warning has been issued for parts of Wales, as well as London, the South East, East and South West of England although most of the UK will see some rain. Temperatures will struggle to get above 17C (62.6F) - well below average for August.
Scotland, where it is not a bank holiday, will enjoy the best of the weather tomorrow.
The Met Office said: "Heavy rain is expected to affect many southern areas of Britain at times during Bank Holiday Monday, with strong winds a possible additional factor close to southern coasts.
"The public should be aware that there may be some impacts to holiday traffic and other outdoor activities.
"A complex area of low pressure looks like bringing an unpleasant day's weather to much of the south on Monday.
"Rainfall amounts look like exceeding 20mm quite widely, while a few places might see around 40mm, so there will be a lot of surface water and spray on roads.
"The spray will probably be made worse by strong winds across some southern areas; gusts to around 40mph may occur at some coastal locations although this will depend on the exact track of the low pressure."
More than five million people in the UK are planning an overnight holiday trip this weekend, VisitEngland said.
While around one million people are expected to be drawn to Notting Hill Carnival, one of Europe's biggest street carnival events, which will see hundreds of musicians and dancers join floats for a procession through west London today and tomorrow.