Forecasters are warning areas of southern Britain already affected by flooding could see a month's worth of rain in coming days. Thousands of people are already struggling to cope after weeks of storms.
Another big storm at the weekend is expected to drop 70 millimetres of rain on saturated catchments and gale-force winds of up to 140km/h are also expected to arrive on Wednesday.
About 1000 homes have been evacuated along the Thames and 14 severe flood warnings are in place along the river and in Somerset. Further evacuations are taking place in the Staines and Egham area. Some 1600 troops are on standby to help, the BBC reports.
Prime Minister David Cameron visited affected areas and said the floods are a huge challenge.
"The government will do everything it can to co-ordinate the nation's resources. If money needs to be spent it will be spent, if resources are required we will provide them, if the military can help they will be there. We must do everything, but it is going to take time to put these things right."
More than 5000 properties have been flooded in the past seven weeks, in the wettest winter in England since 1766.
Labour leader Ed Miliband said flood defences should be made a higher priority by the government.
Mr Cameron has cancelled a planned trip to Israel next week to deal with the crisis.