Britain is set to be battered by 60mph winds and a "month's worth of rain" in a major U-turn following the record-breaking heat-wave.
A day after many in the UK were basking in 27C, today sees a deep area of low pressure bringing gale force winds - with a weather warning issued by the Met Office.
Much of Northern Ireland is subject to the yellow wind warning in place between 10am and 9pm, which threatens loss of power and transport disruptions.
BBC forecaster Helen Willetts said such weather is "unusual for this time of year" and will be felt across much of the country.
While there are concerns 100mm of rain could strike on Saturday and Sunday in Scotland and Northern Ireland.
She said Friday may even "few rumbles of thunder in eastern areas first thing" before the downpours strike.
Temperatures are expected to drop into the teens and lower as a narrow band of rain "tears through quite quickly" eastwards today - more noticeable in the north than the south.
"But even when it clears, sunny spells will be quickly followed by showers, packing in thick and fast in the north and west but anywhere could be heavy with the odd rumble of thunder," continued Ms Willetts.
England and Wales could see 40-45mph winds inland, the meteorologist said, while Northern and Scotland could see "up to 60mph".
"Very unusual and making it feel much fresher," she added.
And that weather continues into the weekend as the deep area of low pressure hangs over Britain "throwing further rain" across Northern Ireland and Scotland.
"The concern here is we'll soon have about a month's worth of rain, 100mm in places," said Ms Willetts.
"And again, that's an awful lot of rain to contend with."
Sunday is expected to have fewer showers, with wind easing and the south feeling a little warmer.
Britain saw the hottest day of the year record broken twice on Tuesday and Wednesday, with the latter hitting over 28C.
UK 5 day weather forecast
Today:
Rain over northern and eastern parts clearing for most during the morning. Some heavy rain for Scotland. Brightening up then but some showers developing and further rain arriving into northwest Scotland. Cooler than recently and windier, particularly for Northern Ireland.
Tonight:
Staying windy with showers continuing to feed in from the west and more persistent rain for northwest Scotland. A cooler night than recently.
Saturday:
Another windy day, particularly across Northern Ireland, southern Scotland and northern England. Showers for many though these dying out from the west later. Persistent rain for west Scotland. Cooler again.
Outlook for Sunday to Tuesday:
Southern areas dry, fine and increasingly warm. More changeable in the north, especially north-west, with some fine weather but also cloudier, windier spells and outbreaks of rain here at times.
