The Treasury will cover the cost of council tax rebates for flooding victims in England, David Cameron announced as he warned that recovering from the crisis would be a "very long haul".
Some local authorities have announced plans to exempt residents forced out of their homes from part or all of the bill.
The Prime Minister, who visited Pembrokeshire and Somerset as he continued his tour of flood-hit parts of the UK, said councils which make the move will not lose out.
He tweeted: "I can confirm we will fund councils that give council tax rebates to people whose homes have been flooded."
A £4 million fund will be made available to councils to cover the bill for giving residents a rebate while they are out of their homes but it will be up to local authorities to decide how the scheme would work.
Councils will not be forced to introduce the payment exemptions, but a No 10 source said the "funding is there so there is no reason why it should not be taken".
They added: "We are sure councils will be very eager to do all they can."
T he funding pot is open to English councils and comes alongside business rate relief for flood-hit communities.
Somerset County Council has already announced plans to suspend the county council part of the tax for residents affected by the flooding and Aylesbury Vale District Council i n south Buckinghamshire said households can apply for a 100% reduction in the fee.
On a visit to Somerset, Mr Cameron said it could take six weeks to clear water from the flooded area.
He told Sky News: "People here are very depressed by how long it's going to take to drain the water away. But what is encouraging is that there is now a new pumping strategy which is going to increase the amount of water pumped out of the Somerset Levels and into the rivers, into the drains."
The Prime Minister stressed that "we have thrown everything at this national effort" to make sure there were as many pumps as possible.
"The advice I have is this will take six weeks to clear. That is a very long time for farmers to be off their land, for communities to be effectively cut off, for some people to be out of their homes.
"It's a very long time, it's a long haul. That's why I keep coming down here to ask is there anything more we can do? Is there more pumping, are there different strategies?
"We should keep asking those questions and doing what we can."
Mr Cameron, who has expressed concern that councils had initially been reluctant to call in the Army, said: "I think you sometimes get a nervousness about who will pay for this, and a nervousness about admitting that you can't deal with this without military assistance.
"But, when you have something as big as this, what you need is a vast national effort, co-ordinated as it has been from the centre through the Cobra emergency committee and drawing on every single thing that you've got: whether that's money, whether that's military, whether that's pumping, whether it's enhancing the emergency services, everything that can be done needs to be done."
In a further indication of the ongoing disruption caused by the severe weather, Network Rail said the storm-damaged main line at Dawlish is not likely to be completely repaired until mid-April.
Originally, Network Rail said the stretch of line - an important link between London and the far South West of England - would not be repaired before March 18.
Some 84 flood warnings remained in place across England and Wales alongside the two severe flood warnings - meaning there is a danger to life - on the Somerset Levels.
The Environment Agency (EA) said there is an on-going risk of flooding from the Thames where several hundred properties have been flooded since January 29.
There was ongoing river flooding on the Thames in Windsor and Maidenhead, Surrey, Buckinghamshire, Wokingham and West Berkshire and the EA said the Thames Barrier would close to hold back the incoming tide.
EA flood risk manager Kate Marks said: "Our thoughts go out to those communities dealing with flooding. Although it is currently an improving picture across most of the country we will continue to see the impacts of flooding for many days to come."
Wales's Natural Resources Minister Alun Davies said: "I am encouraged to see the Prime Minister visiting Pembrokeshire today to see at first hand how we have successfully managed the impact of flooding in Wales. We have noted with interest his suggestion that there may be further financial support available to help with the clean-up.
"We assume that as the PM chose to make this announcement in Pembrokeshire, not England, there will be additional funding for Wales and our officials are following this up as a matter of urgency. We would want to make sure extra funding is used to best fit local circumstances.
"I'm sure the PM will have been impressed by what sustained investment in flood defence can achieve. A recent report showed that in Wales our investment helped protect 99% of properties at risk of flooding."
A Local Government Association spokesman said: "Many people contending with flood damage to their homes have already been offered council tax rebates by their local authorities.
"Council budgets are stretched and demand for support is high, so it is good news that Government will be supporting local authorities' efforts to provide financial support to flood-hit homes.
"Local authorities are keen to work with Government to ensure the application process is straightforward and that the benefit quickly gets to where it is most needed."