Storm Callum will ease off today today after claiming the lives of three people.
The south east, which has so far escaped the torrential downpours of the last 48 hours, will experience muggy conditions overnight with temperatures in the high-teens.
But the rainfall which has plagued western Britain will make its way east as the day progresses, weakening as it does so, meaning by the afternoon there will be a “reversal in fortunes”, the Met Office said.
“The areas that have seen the bulk of the sunshine over the last couple of days will then be under the cloud, with patchy, light rain and drizzle at times,” said meteorologist Simon Partridge.
“Those areas further west which have seen huge amounts of rain will finally turn drier, brighter, with some decent sunny spells developing by the end of the day on Sunday,” he added.
Scotland and Northern Ireland should largely have dry, clear conditions through Sunday.
As Sunday dissolves into Monday, cloud and patchy rain will remain in the south east, with generally clear, dry conditions further north and west.
“There’s a cool clear start for many parts of the UK on Monday, and actually for much of the UK it’s a dry fine and sunny day to boot,” Mr Partridge said.
The clouds and patchy rain will remain over the south-east corner of the UK until the early hours of Tuesday with a drier, cooler outlook expected for the week, he added.
Storm Callum caused travel misery and flooding as rivers burst their banks and power supplies were wiped out for many across western parts over Friday and Saturday, with south Wales the worst-hit region.
A man died after a landslide struck on Saturday near the village of Cwmduad in Carmarthenshire, west Wales.
The victim, whose age was not given, died at the scene on the A484, Dyfed-Powys Police said.
The east and south east escaped the storm’s wrath and enjoyed largely sunny, warm conditions.
Donna Nook in Lincolnshire reached 26.5C on Saturday, making it the warmest October day in seven years.
Three-day weather forecast:
Today (Sunday): It will be a largely overcast and wet morning across the UK, with heavy rain or showers for much of England, Wales and Scotland.
Rain will clear to the east through the day, turning showery at first, but then brighter and cooler with sunshine behind. A largely dry and fine day for Northern Ireland.
Tonight (Sunday night): A rather wet and cloudy night in the far south-east of England with rain throughout. Elsewhere, it will be dry for much of the night, with clear spells in central and western parts.
North-west Scotland will see showers, and it could become damp along the rest of the west coast into the early hours.
UK Outlook (Monday and Tuesday): There will be rain in the far south-east of England on Monday. North-west Scotland will see showers throughout. Elsewhere, it will be largely fine and dry with bright spells of sunshine.
Unsettled on Tuesday, with gales in northwest Scotland and outbreaks of rain for many. Drier in central parts.