Photo from the-celebrity-report.blogspot.com .

LONDON (AFP) – Weather forecasters on Thursday were predicting a cloudy but dry start to the royal wedding day, with only a small risk that rain may dampen the proceedings.

People camping out to secure a prime spot for the big event could be in for some light showers, but any overnight rain should clear by the morning, the Met Office said.

More than one million extra visitors are due to descend on London to witness the marriage of Prince William and Kate Middleton on Friday, while street parties are being held across Britain.

The capital is expected to be largely dry but cloudy in the morning, with a 10 percent risk of showers.

Andy Page, chief forecaster at the Met Office, said: “After a cloudy start to the day, with a 10 percent chance of a shower, we should see some sunny spells developing over London during the morning.

“The chance of a shower increases to 30 percent for the London area around lunchtime as temperatures reach 17 Celsius”.

Warmer temperatures still were forecast for the afternoon, rising to 19 degrees Celcius in the sunshine.

MeteoGroup, meanwhile, gave a gloomier outlook, putting the likelihood of showers across London at 80 percent — or 40 percent in any one spot — and warning of possible thunderstorms across south-east England.

“As is the nature of showers and thunderstorms, one location can receive torrential rainfall whereas somewhere just a few miles away can stay completely dry with sunshine,” said MeteoGroup forecaster John Hutchinson.

“This means that predicting whether rain will occur during the ceremony and subsequent events is impossible at this stage. All that can be said is that there is a chance of showers.”

If the rain holds off the royal couple will travel from Westminster Abbey to Buckingham Palace after the ceremony in the 1902 State Landau — an open-top horse-drawn carriage

But if the heavens do open during the church service, they will take the Glass Coach used by William’s mother Princess Diana to travel to her wedding to Prince Charles in 1981.

Wedding spectators were undeterred by the forecasts, with hundreds of tents pitched along the processional route on Thursday, as well as at dedicated camping sites, such as Clapham Common.

Rachel Burden, an off-duty police officer camped on The Mall, said : “We are used to unpredictable weather, we’ll be ok.”