However, skies could clear in Leeds in time for England’s Euros clash with Denmark, forecasters have said.
Met Office meteorologists have predicted grey skies and rain across the entire nation throughout the day, but said sunshine could break through the clouds in time for the 8pm kick off.
Met Office forecaster Annie Shuttleworth said the heaviest showers are likely to settle in the north-east and south-western corners of England on Wednesday.
She added that up to 50mm of rain has been predicted for the worst-hit region of North Yorkshire.
Ms Shuttleworth said: “It’s quite a messy picture – there’s a lot of rain going on.
“We are seeing generally unsettled conditions across the whole of the UK with heavy showers in the South and South East.
“On Wednesday morning we will see clouds break out and heavy showers, many across the South East through the mid-morning onwards.
“By early evening showers will start to die away.
“The sunnier and drier spells will be much more likely by 8pm – though there is still a risk of rain.”
Four flood alerts, for areas where flooding is possible, have been issued for isolated spots in Hampshire, Berkshire, and Shrewsbury by the Environment Agency.
The Scottish Environment Protection Agency (SEPA) has also issued alerts for areas where rain could cause travel disruption for Dundee and Angus, Fife, Findhorn Nairn Moray and Speyside, and Tayside.
Wednesday highs of 20C (68F) are predicted in London, Edinburgh, Cardiff and Belfast.
Met Office forecast for Leeds on Wednesday:
10% chance of rain at 8pm
19 degrees temperature expected
Rain to ease in Leeds by 3pm
'Light showers changing to cloudy by late morning'