(CNN) - Everything has been meticulously planned down to the final detail.
But there's one thing that even royalty cannot control come wedding time -- the weather.
Fortunately, it looks like Britain's Prince Harry and Meghan Markle have received a wedding gift from Mother Nature in the form of a perfect forecast for their big day Saturday.
Weather in Great Britain can be notoriously fickle, and London averages around 10 days of rain during the month of May.
But with each passing day, the forecast looks clear, and the fears of a rain-soaked wedding day are all but gone.
On Saturday, a few early clouds will mix with the sun in the morning, but will give way to a mostly clear sky with plenty of sun and temperatures climbing to a mild 20 degrees Celsius (68 F), slightly above the average of 18 C (64 F) for the date.
Temperatures will be seasonably cool in the morning, with a low around 8 C (46 F), but it will warm up quickly with ample sunshine.
While the chance of rain isn't zero, it's pretty close, with the possibility of a stray morning shower popping up at around 10%.
A dry wedding day is in line with other British royal nuptials, including those of Prince William and the former Kate Middleton in April 2011 and Charles and Diana's in July 1981. Those both avoided the damp conditions many associate with British weather.
Warm and sunny for outdoor festivities
The ceremony will take place indoors at noon (7 a.m. ET) in St. George's Chapel at Windsor Castle, but there will be outdoor appearances and events throughout the day.
More than 1,000 members of the public will share in the festivities outside the chapel from the grounds of Windsor Castle.
After the ceremony ends, the newlyweds will head outside for a 2-mile procession expected to take around 25 minutes, with crowds lining the route.
At that time, temperatures should be near the high of 20 C (68 F) under sunny skies, which will make it feel even warmer without shade.
While weather-hardened Britons would have likely tuned up in huge numbers even if the forecast called for torrential downpours and gusty winds, the expectation of perfect weather will likely mean an even larger turnout.
A cold rain didn't keep hundreds of thousands from celebrating Queen Elizabeth II's diamond jubilee in London in June 2012, with 20,000 people taking to boats to participate in a giant flotilla along the Thames.
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