While the sun may be shining on Team GB's cyclists after their historic results in the Tour de France, there is a risk of showers for London on the day of the Olympic opening ceremony.

While Danny Boyle's ambitious plans for the opening ceremony include clouds that will rain down over the stadium in Stratford, east London, fingers had been crossed that the much-anticipated event would otherwise stay dry.

After weeks of wet weather the outlook has brightened for the coming week.

The mercury is set to rise to 29C (84F) or perhaps 30C (86F) tomorrow, and will stay in the high 20s for the rest of the week, but forecasters said temperatures are set to fall again by Friday.

Billy Payne, a forecaster with MeteoGroup, the weather division of the Press Association, said: "Today is looking to get up to 27C (80.6F) or 28C (82.4F) in the South East and it will be dry, hot and sunny in most parts of England and Wales.

"But there will be a lot of cloud across southern Scotland and Cumbria, with persistent rain.

"Tomorrow will be more of the same and could get up to 29C (84F) or 30C (86F) in the London area.

"Towards the end of the week it is going to get a lot cooler and more unsettled.

"It looks as though there's a risk of heavy showers, certainly in the south-east corner of the country.

"Temperatures should still be somewhere around the mid-twenties on Friday, and it is likely to be cooler over the weekend."

Widespread flooding, the wettest period of April to June on record and more heavy rain so far this month have been caused by the jet stream settling unusually far south.

But forecasters said it is on its way back north, leading to more traditional summer weather this week.

Bookies have been taking bets on what the next few weeks will bring, with William Hill offering odds of 3/1 that it is raining during the opening ceremony and 66/1 that the Olympic flame is extinguished while the last person carries it into the stadium.

They are also offering 12/1 that a temperature of more than 100F (38C) will be registered in the UK while the Games are taking place.

William Hill spokesman Rupert Adams said: "There can be little doubt that the British weather will have its say at the Olympics, most likely it will be wet but we could be in for a scorcher."