Rain may fall on the King’s parade after his coronation, as forecasters expect showers on Saturday.
The Met Office said it is quite difficult to say what exactly the weather will be like with any certainty.
But it looks as though it would be a good idea for royal fans to wear their raincoats and take their brollies.
Met Office spokeswoman Nicola Maxey said: “We’ve got quite a showery picture. Friday is going to be a mixture of heavy rain and showers and thunderstorms.”
She said London may stay dry on Saturday morning, but that showers may develop through the afternoon.
The coronation ceremony at Westminster Abbey will end at 1pm and the newly crowned King and Queen will begin the procession back to Buckingham Palace in the gold state coach.
Some 4,000 sailors, soldiers, aviators and other military personnel from across the UK and the Commonwealth will accompany Charles and Camilla on their return procession.
There will be more than 1,000 route liners from the Army, RAF and Royal Navy.
Charles and Camilla are expected to enter Buckingham Palace through the centre arch at 1.33pm.
They will receive a salute from the military in the palace gardens at 1.45pm, and then at about 2.15pm they will be joined by members of the royal family on the palace balcony to watch the flypast.
Ms Maxey said: “At the moment it looks like, as I say, the morning should be relatively dry with some sunny spells in London, but the afternoon could see showers developing in London.
“But long lead time, so as always the message is to keep an eye on the forecast and check it regularly because the detail will become clearer as we get nearer to the day.”
Meanwhile, it is expected to be warm and humid with temperatures reaching as high as 20C.
“We could certainly see temperatures, high teens, maybe 20C for London, and mid to high teens for elsewhere in the country as well.
“Whether you feel warm or not will depend on whether you get a break in the cloud and a spell of sunshine.
“In which case it’s going to feel great, but under a shower it might not feel as nice,” Ms Maxey said.
