Royal wedding enthusiasts – it’s going to be a wet one.

The tens of thousands of followers who are expected to throng the outdoor venues hosting events for the nuptials of Prince William and Kate Middleton, have been told to pack a brolly, as wet weather is almost certain to put a dampener on the big day.

Forecasters are predicting the end of the spate of recent sunshine that has cast over London, and a return to “more typical April weather”, with showers tomorrow morning in the capital before a clear period and then more rain. There is even a risk of thunderstorms, with the top temperature expected to be 19C (66F).

The Met Office has warned a north-easterly wind could make it feel  “rather chilly” when the sun goes in.

“We can expect a lot of cloud and a breezy day – I think there is a chance of some showers coming through as we go into the afternoon,” a spokeswoman said.

Some of the official guests of the wedding are expected to arrive at Westminster Abbey as much as three hours before the start of the service at 11am but they have been warned there are no toilet facilities in the abbey.

After the general congregation arrives between 8.15am and 9.45am, various world leaders and other guests will begin to pour in. All of those in attendance, including visiting royalty, celebrities, friends and family, will have their identification checked and go through security screening before entering the venue.

If the weather conditions turn out to be favourable, the newlyweds are due to leave the abbey in an open-top 1902 State Landau carriage for the 20-minute ride to Buckingham Palace. In the event of rain, they will travel in a glass coach.

Thousands of people are expected to line the parade route and motorists have been warned to avoid central London, as a number of roads will be closed from 6am tomorrow.

These include part of Charing Cross Road, Horse Guards Road, The Mall, Parliament Square, Millbank, The Strand, Embankment, Westminster Bridge and Whitehall.