By Brandon Miller, CNN

(CNN) -- The final countdown is on and everything has been meticulously planned down to the final detail.

But there is one wild card that even the Queen herself cannot control: What will the weather be for Prince Harry and Meghan Markle's big day on Saturday, May 19?

Since we are still 10 days out, it's still too early to make a definitive call on rain or give detailed predictions about the timing of any potential showers -- but we can look at the long-range weather models and get an idea of what the general weather pattern will be while the world's eyes are on England.

May's weather is off to a perfect start, with clear skies and well-above average temperatures in London nearing 30˚ C (86˚ F), which has locals feeling the royal wedding fever.

The average high temperature for May in London is 18˚ C (64˚ F), so this past week has felt downright summer-like.

A change in the weather threatens to dampen spirits, however, with cooler temperatures and several bouts of rain moving through in the next week as we lead up to wedding weekend.

Temperatures will plummet to below average with significantly more clouds and some rain in the forecast as a couple of low pressure systems move through the British Isles next week.

Fortunately, the weekend looks like it could see a return of the milder air and potentially clearer skies as high pressure builds over the North Sea.

According to the UK Met Office, the nation's weather forecasting service, "there is low confidence in the forecast for the rest of next week and the following weekend, but there are some signals that it may turn drier, more settled and somewhat warmer with light winds."

The forecast for the day can, and likely will, change over the next week and a half. Weather forecasts more than a week out have considerably less skill than short-term forecasts of just a couple of days.

Especially when dealing with a region that has rapidly changing weather conditions like Great Britain.

A dry wedding day would fit in line with other recent royal nuptials, including those of Prince William and Catherine Middleton in April of 2011 and Prince Charles and Diana's in July, 1981, both of which avoided the damp and rainy conditions many associate with British weather.

What if it rains?

Historically, the month of May in London will have around nine days with measurable rainfall.

And with unsettled weather expected next week it is certainly possible there could be showers still around on Saturday.

What would that mean for the royal wedding?

Likely not a lot for the ceremony itself, which is taking place indoors in St. George's Chapel at noon (7 a.m. ET).

But more than 1,000 members of the public will get to share in the festivities outside of the chapel from the grounds of Windsor Castle.

After the ceremony has ended at 1 p.m. (8 a.m. ET), the newlyweds will head outside for a two-mile procession that is expected to take around 25 minutes, with large crowds lining the route.

Rain would certainly hamper these outdoor festivities, but if history is any indication, it will take more than just a steady rain to keep the crowds from enjoying this much-anticipated event.

A cold rain didn't keep hundreds of thousands from celebrating Queen Elizabeth II's diamond jubilee in London in June of 2012, which featured 20,000 people taking to boats to participate in a giant flotilla along the Thames.

If it does rain, according to superstition, it means good luck and fertility for the newest royal couple.

Be sure to check cnn.com/weather for the latest forecast for London, and even the weather for your local royal wedding party.