The risk of a dam collapsing and inundating a number of villages reduced overnight but the danger is not over.
A major operation continued through the night to reduce water levels at Ulley Dam, near Rotherham, South Yorkshire, and rebuild parts of the dam wall.
On Tuesday, around 700 people were evacuated from their homes following fears that the dam might fail following unprecedented rain and the appearance of "areas of weakness".
A busy stretch of the M1 was closed due to concerns about the dam, causing 15-mile tailbacks, and remained shut on Wednesday morning.
Police and other agencies were meeting to decide whether the motorway can reopen.
As 17 huge pumps sucked 11 million gallons of water an hour out of the swollen Ulley Reservoir, almost 100 people from downstream villages spent the night at makeshift rest centres.
Hundreds of others were not allowed to return to their homes and stayed with relatives or friends.
A Rotherham Council spokesman said: "The risk of a major breach remains significant but the situation is currently stable."
But the council's strategic director Adam Wilkinson said the risk was reducing. Mr Wilkinson said the water level in the reservoir has dropped by about half a metre (19 inches) since the pumping began. Engineers are aiming for a two-metre (6ft 6ins) drop to reduce pressure on the dam walls.
On Tuesday, firefighters from all over Britain were brought in with the massive pumps, which have the pumping power of 100 fire engines. As the operation at Ulley continued, water levels began to drop slowly in surrounding villages which were some of the worst hit by the flooding of the last few days.
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