The Prime Minister, who launched a new Points of Light award to recognise voluntary work, told some of those who helped the country cope with the floods to keep up their efforts in case there are similar crises in the future.
At a reception in Downing Street, Mr Cameron announced £500,000 of funding for community foundations and confirmed that £4 million from the Libor fines levied on banks would be directed to rescue organisations.
He said: "There were moments when it felt like the whole country was under attack in terms of the weather and it was never going to relent.
"But while we saw the worst of British weather, we saw the best of British spirit."
He said it was a "privilege and an honour to travel the country and see that spirit first hand: whether it was Facebook sites to clean up Chesil Beach, whether it was community cafes in Somerset, whether it was Scouts, Guides and others pitching in, whether it was a group of young Muslims from right across the country, including from Yorkshire, who went all the way down to Somerset".
Mr Cameron, who has said he "very much suspects" that the floods were due to climate change, warned the volunteers they may be called on again.
"Please keep at it," he said. "I hope we won't have weather quite as bad as that but the fact is we have seen more extreme weather events, we have had things that we have been told are one in a 100 or one in 200-year events and they seem to be happening more frequently."