It comes as high pressure is forecast to settle over the UK, causing clear sunny spells but also morning temperatures hitting zero in some parts of the country. Some Britons will see some stubborn fog patches on Thursday, though most parts of the UK will be clear and dry with light winds, the Met office said.
However, temperatures will remain in the single figures for most, according to BBC weather maps.
They show London should average just nine degrees Celsius by the mid-afternoon, with central Scotland as low as 5C.
By the evening, a weather front is expected to make its way towards Britain from the north-west.
Weather maps indicate this will bring cloud to north-western areas of Scotland and Northern Ireland.
For today the Met Office forecast: “Cloudy in the far south, perhaps with a little rain at times. Rather chilly for many.”
For Thursday night, the forecaster added: “Some rain for northwest Scotland. Perhaps cloudy with a little rain in the far south of England.
“Turning frosty elsewhere with freezing fog patches, perhaps dense in places by dawn.”
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For Friday afternoon Ms Powell warned some of the fog will “really struggle to clear”.
She said: “There’s not much breeze set to work on it, and the sunshine isn’t particularly strong at this time of year.
“If the fog does stick, temperatures [of] two, three degrees are possible.
“As for the weekend, I suspect fairly similar temperatures and a fairly similar-looking picture overall. Some chilly nights to come.”
Meanwhile, A flood warning remains in place at the time of writing for Keswick Campsite, according to the government’s flood warning information service.
For the weekend, the high pressure likely to remain in place over the UK before slowly shifting east, the BBC said.
This will keep temperatures cold yet dry, though some cloud and damp can be expected in northern Scotland.
As the high pressure moves away, rain could also spread into some western areas.
For Europe, tomorrow will see a large area of high pressure over central parts of the continent but southern parts of Portugal and Spain are set for wet weather.