Some of the UK has had more than a month’s rainfall in just a few hours as thunderstorms took hold following the long summer heatwave.
The Met Office upgraded a weather warning for Northern Ireland to amber, saying damage to buildings from flooding and lightning strikes is likely.
Belfast International Airport saw 88.2mm of rainfall on Saturday afternoon, above the July average for the entire region, which sits at 81.2mm.
Roads have flooded and transport has been affected, with some buses cancelled.
Meteorologist Sarah Kent said that, unlike thunderstorms in many other parts of the UK, those in Northern Ireland are as a result of low pressure, rather than directly related to the recent heatwave.
Heavy, thundery showers are continuing in western areas as well as parts of Wales, the Met Office said, as changeable weather replaces the hot spell much of the UK has endured for weeks.
“It’s a very unsettled weather picture across the whole of the UK,” said Ms Kent.
Short Ferry in Lincolnshire had 41.8mm of rainfall in one hour on Friday, nearing the county’s monthly July average of 55.8mm.
The searing temperatures which had reached the mid-30s in southern parts of the UK have dropped, in some places by up to 10C.
Saturday’s highs are expected to peak at 24C in central and southern England, 20C in Scotland, 19C in Wales and just 18C in Northern Ireland.
Similarly cool weather is expected on Sunday, and a yellow weather warning for rain and wind is in place for Wales and southern England into the afternoon.
Wind speeds of up to 40mph inland are expected, and campers have been warned to take precautions.
Ms Kent said: “The warning is in place particularly for holidaymakers who are out camping or towing their caravans, they are going to see some very strong gusts.”
While some will have welcomed the rain and the cooler temperatures, those keen to catch a glimpse of the blood moon, the longest lunar eclipse of the 21st century, on Friday will have been disappointed.
The cloud cover meant the rare celestial event was not visible to many in Hampshire and Wiltshire in the South and South West, to Hull in East Yorkshire, Liverpool in the North West and Dublin in Ireland.
Holidaymakers have been beset by delays and cancellations due to the extreme weather.
A number of flights have been affected, and travellers have suffered long delays for ferries and cross-Channel trains.
Singer Sir Tom Jones was forced to cancel a concert due to the wet weather.
York Racecourse tweeted on Friday that the show had been called off because of the “thunder and lightning storms”.
Tony Wafer, RNLI community safety manager, said: “If you are heading to the coast this weekend, please find out where your nearest lifeguarded beach is and ask the lifeguards for advice on conditions, especially if you are going in the water.
“RNLI lifeboats and lifeguards have had four times as many rescues of inflatables so far this summer than they did last year.”
Meanwhile, police forces have been called following concerns for people’s welfare at rivers and a lake.
Thames Valley Police said a man’s body was recovered from the Jubilee River in Slough, adding that his death is not being treated as suspicious.
Warwickshire Police said emergency services personnel searching for a 17-year-old boy who disappeared after getting into difficulty in a quarry lake in Bishops Itchington, near Leamington Spa, have recovered a body.
Essex Police said a body was found on Saturday in the search for a boy who was last seen in the sea near Clacton Pier two days earlier.
The force was called on Thursday amid concerns for the welfare of two teenagers and was on the scene just after 6.35pm.
One boy was rescued by a lifeboat crew, and police said the body of a 15-year-old – provisionally named as Ben Quartermaine – was recovered shortly before 8am on Saturday.
Bedfordshire Police are also looking for a man who got into difficulties in the River Great Ouse on Friday afternoon.
The heatwave, which last week contributed to a “high” air pollution alert being issued for London, is set to return towards the end of next week.
“We will see more settled conditions across southern areas by the weekend, with temperatures creeping back towards 30C in places,” said Ms Kent.