Brits are set for a colder end to the week as mourners queuing to pay their respects to the Queen at Westminster Hall, in London, may see temperatures drop to single figures over night.
A northerly wind combined with a high pressure system are behind the cooler feel across the country although there will be less rain than there has been in recent days.
Thousands are aiming to see the Queen lying-in-state in Westminster Hall before the period ends at 6.30am on Monday morning and will be exposed to the elements as they wait in a 10-mile-long queue.
Viewing will be open 24 hours a day and in the early hours of Friday morning it will feel cold, says the Met Office, while urging people to "make sure you are prepared".
Thursday will be "a mostly dry" day that is rather cloudy at times but still with some bright or sunny spells, according to Met Office forecaster Simon Partridge.
He said: "The main thing is people can be staying dry, with some light northerly winds, but that will mean it will start to feel a little bit fresher as the day moves on."
Thursday should see top temperatures of 20C to 21C which is "pretty pleasant and nothing too hot or too cold for those who are standing around for a few hours, but the main thing is that they will be dry".
A "fresher feel" will be more noticeable by night-time but it will "start to feel a bit chillier" overnight into Friday as temperatures drop to around 9C to 10C.
Mr Partridge said: "If you are standing around for a few hours then you will definitely need to wrap up a bit warm."
And over the weekend while "no significant" rain is forecast for London it will be chillier with temperatures in the mid to late teens.
Mr Partridge added: "It will not be wall-to-wall sunshine. There will be sunny spells through the days and clear spells overnight, but gradually it will get a little bit cooler each day."
With well-wishers set to wait for hours in lines stretching along the banks of the River Thames, the Department for Digital, Culture, Media and Sport has set up an online tracker to help them see how long the queue is.
Network Rail has said services and stations are likely to be "extremely busy" during the official mourning period.
Short-notice changes may be necessary and people should check live travel information before and during journeys.
UK forecast for the next 5 days
Fine for many today, cooler and windier Friday.
Today:
Fine with sunny spells for many. Cloudier with some showers across Northern Ireland, some eastern parts of England and, more especially, northern Scotland where some heavy showers. Breezy, especially in the north, and less humid than yesterday in the south.
Tonight:
Further showers across northern Scotland with North Sea coastal areas in England then also turning showery. Also a few showers in the far west. Breezy and colder than last night.
Friday:
Showery in over northern Scotland and, more especially, North Sea coastal areas in England where some heavy showers. Otherwise, many areas fine and dry. Windy and cooler than today.
Outlook for Saturday to Monday:
Generally fine and dry with variable cloud and sunny spells. Blustery showers for some eastern coastal areas, especially at first. Cool, with patchy overnight frost in rural areas..
