Dry and sunny weather on Friday and Saturday is expected to give way to widespread heavy rain and strong winds on Sunday and more wet conditions on Bank Holiday Monday.

Bookmakers Ladbrokes have slashed the odds on the bank holiday being the wettest in history from 50/1 to 20/1 following a flurry of betting. Spokesman Nick Weinberg said: "Workers across the country have been looking forward to a sunny bank holiday. But a number of our customers seem convinced we're in for a wet weekend."

Jeremy Plester of MeteoGroup UK, the weather division of the Press Association, said: "(Friday and Saturday) are the lull before the storm and I'm afraid the rest of the weekend is going to be something of a washout."

He said that the rain was expected to sweep in from the west by Saturday night accompanied by strong winds from the north.

Mr Plester went on: "It's going to be grim with just about everywhere in England and Wales getting heavy rain pretty much throughout Sunday. It may be drier and brighter for some northern areas on Bank Holiday Monday, but elsewhere there will be heavy rain again. We could see some temperatures over the holiday weekend struggling to reach even 10C (50F)."

Around 1.9 million Britons were escaping the gloom at home by flying abroad over the weekend, according to the Association of British Travel Agents. Spain and its islands were the favourite destinations for short-haul travellers, with Florida the most-popular long-haul spot. The top five city-break destinations were Paris, Amsterdam, Dublin, Rome and Prague.

If the forecast rain arrives, Britons will have to contend with the second successive bank holiday wash-out as the May Day break on May 7 was wet. Also, for the second time this month, poor bank holiday weekend weather has followed a dry and warm snap.

Despite the forecast, the AA said around 18 million vehicles were set to take to the roads during the weekend. Traffic on Bank Holiday Monday is expected to be 10% busier than it was on May Day Bank Holiday Monday.

The worst spots for jams are expected to be the M25, the M1 northbound, the M4 westbound, the M6 through the West Midlands and north of Manchester and the M5 in the Midlands and southbound around Bristol.