It could take more than 24 hours for the flood water in Oxfordshire to drain away, even though no rivers are rising, the Environment Agency said.
Oxford's water levels have started to subside
The agency said tributaries draining into the River Thames mean levels stay high even once it has peaked.
Two severe flood warnings remain but most properties are now out of severe danger of flooding, the agency said.
Although, 260 homes in the Vicarage Road area of Oxford are still without electricity.
Southern Electric turned the power off because incoming cables were left underwater.
The supplier said it is monitoring the situation but is unable to restore the supply until water levels have dropped.
In total, about 900 homes have been flooded in the county since torrential rain hit the Thames Valley a week ago.
A Henley regatta stand was swept away (Julia Reichel/oepkes.com)
About 150 homes in Oxford were flooded on Wednesday after Thames tributaries burst their banks, spilling on to the river's already water-logged flood plain.
In Abingdon some 570 properties were flooded.
The remaining "severe flood warnings" are for Oxford and Abingdon, while the River Ock - from Charney Bassett to Abingdon - has been downgraded to a less severe "flood warning".
Two of the main roads into Oxford, Botley Road and Abingdon Road, as well as a number of smaller roads, remain closed.
Local authorities in Oxfordshire have joined forces with the British Red Cross to launch a national flood relief appeal fund.
The Bishop of Oxford has also launched an appeal to help with the relief efforts in the aftermath of the floods.