Britain is bracing for a drenching as the weather turns cooler and wetter today.
Downpours are forecast in Wales, the Midlands and northern England, and set to get heavier throughout the afternoon.
Parts of Yorkshire and Lincolnshire could see up to 32mm of rain an hour, with showers also predicted in northern Scotland.
The Environment Agency is warning of possible flooding in eight locations, including Alton, High Wycombe, the Lambourn Valley and Salisbury Plain.
It's set to be a chilly start to the day, particularly in the southeast, where households could even wake up to frost.
However, the mercury is set to rise throughout the day, reaching highs of 17C in London and Southampton, 11C in Belfast and 10C in Edinburgh.
Southern parts of Wales and England will be spared the worst of the rain, with dry and sunny weather which will turn cooler later in the day.
Giving the latest forecast, a Met Office spokesman said: "Through the remainder of the weekend we will start to see it turn more unsettled with the risk of showers developing.
"Overnight we'll see clear skies form any but an increasing risk of showers in the northwest.
"Temperatures on the chilly side, particularly across southeast England a touch of frost is possible first thing here Sunday morning, and any mists and fog patches soon clearing.
"Sunday itself will see a mixture of sunshine and showers across the north of the UK and then across Wales and the Midlands some very heavy showers developing through the afternoon.
"Through Sunday evening the heavy showers will start to ease away but we will see colder air filtering in across Scotland and Northern Ireland with further showers here at times.
"Overnight we'll see some drier weather developing for some too.
"Outlook for next week is turning cooler, wetter and windier."
UK 5-day weather forecast
Today:
Cloudier across Wales, the Midlands and northern England with rain or showers, heavy in places later. Showers also affecting northern Scotland, where cooler. Fine elsewhere, and warm in the south.
Tonight:
Outbreaks of rain moving south across central areas, while further showers will affect northern UK. Staying dry in the south with increasing cloud.
Monday:
Feeling cooler with sunshine and showers in north. Cloud and patchy rain across central areas moving south. Southeast of England will remain warm with some sharp showers during the afternoon.
Outlook for Tuesday to Thursday:
Showers and some longer spells of rain, interspersed with drier and brighter spells. The rain heaviest in the south, with parts of Scotland perhaps largely dry. Temperatures close to average.
