Residents of several flooded villages in West Wales are waiting to see if they can return home after spending the night in community centres.
Around 150 people had to be rescued from their homes and caravan sites after severe flooding engulfed their communities.
The clean-up has begun in villages around Aberystwyth after a month's rain fell in 24 hours.
Fire crews, coastguard lifeboats and military helicopters were all deployed when water swept through several caravan parks and villages.
The Prime Minister joined others in praising the work of the rescue teams and emergency services who ensured there were no serious casualties.
In the 24 hours leading up to the flooding, twice as much rain fell in the area than normally falls during the entire month of June.
It triggered severe flooding in the small hours of Saturday morning at four caravan sites along the River Lery: Riverside, Mill House, Glanlerry and Sea Rivers.
Even an inshore lifeboat team taking part in the rescue operation had to be airlifted, after getting into difficulty attempting to rescue a disabled man from a flooded caravan.
Dozes of people were sheltering in rest centres after being saved from the affected areas, and three people were receiving treatment after suffering minor injuries.
The main streets in the villages of Talybont and Dol-y-Bont also became gushing rivers as a result of the rain fall, damaging dozens of homes.
By Saturday evening, the Welsh Environment Agency had flood warnings in place across three different rivers.
The agency said while most rivers had peaked, concerns remained about parts of the Rheidol, which is still rising, and the River Fathew in Bryncrug.
People in the area have been urged to remain alert to water levels.
Local police said that anyone near the flooded areas in Ceredigion should "keep away from rivers and flood water".
"Although water levels are receding they remain very dangerous," Dyfed-Powys police said.
"Do not take any unnecessary risks for your own safety, and heed the advice of emergency services in relation to road closures."
A Downing Street spokesman said David Cameron had spoken with Wales First Minister Carwyn Jones and Secretary of State for Wales, Cheryl Gillan, to be fully briefed on the flooding.
"Mr Cameron offered his full support to all those affected by the extreme weather and passed on his thanks to the dedication of the RAF, lifeboat crews, emergency and other local services who have worked tirelessly to make people safe and keep disruption to a minimum."
Ms Gillan added: "This has been a very impressive operation in horrific weather conditions and with unprecedented flood levels.
"Those involved in the rescue mission at the caravan parks in Llandre have acted quickly and with courage.
Jason Hughes, who lives near Talybont, told Sky News: "The lower part of my village is completely closed off, people are all in their top bedrooms."
Pat Edwards, 56, whose partner runs Mill House Caravan Park, said she had not seen flooding like it in 50 years.
She added that three groups of guests currently staying at the site had decided to stick the weather out.
"The helicopter has come over and offered to rescue us," she said.
"At the moment, we've got three families here - one is staying in their caravan and two couples are upstairs with us.
"We've got an escape route planned if necessary, if we need to we can climb up the bank and get picked up by the helicopter."
Jenny Evans, aged 42, of Stafford, owns a caravan at the Beachside Park near Clarach Bay.
She added: "One of neighbours, who's known as Nana Dot, had to be rescued from her static caravan this morning.
"She's in her mid-70s and had to be taken in the back of a pickup truck.
"The electricity has been off since about 8am, as there's quite a bit of flooding.
"It's like we've had a month's worth of rain in 36 hours."
A spokesman from the Mid and West Wales Fire and Rescue Service said there had been a large amount of water with a heavy current.
He added: "Numerous people are surrounded by flood water and are requiring rescue by fire service boats, inshore life boat teams and RAF helicopters."
The rain over West Wales had stopped by Saturday afternoon. The weather pattern passed to the east and left the UK, causing some thunderstorms in the York area.