Parts of northern England are being urged to prepare for the risk of significant flooding in some areas from early tomorrow morning, the Environment Agency said.
The Met Office says Storm Christoph is likely to affect the UK and has issued a weather warning from tomorrow onwards.
Several days of persistent, and occasionally heavy, rain are expected.
The heaviest and most persistent rain is likely to be across Wales and the high ground of northern England.
By early Thursday, 30mm to 60mm of rain is expected to have fallen widely across the warning area, with 100mm to150mm over the high ground of Wales and northern England.
Up to 200mm is possible across parts of north Wales and North West England.
Strong winds will also accompany the rainfall and may add to travelling difficulties across areas higher and more exposed routes.
The Environment Agency is encouraging people to sign up to flood warnings and check the latest safety advice as heavy downpours are likely to fall on saturated ground, making the flood risk significant.
The Environment Agency is working with partners across the country to reduce the flood risk brought on by the severe weather conditions.
It said extensive preparations were being made to operate flood defences, flood storage reservoirs and to put up temporary barriers where needed to help protect communities ahead of the incoming weather.
No flood warnings are yet in place for Cumbria.
Katharine Smith, flood duty manager at the Environment Agency, said: “Heavy and persistent rain falling on already saturated ground with snowmelt in parts of northern, central and eastern England is expected to bring significant river and surface water flooding and could cause damage to buildings in some communities.
“Flooding could continue to affect parts of central, eastern and northern England into Friday, with localised flooding of land and roads a possibility elsewhere across much of country on Wednesday and Thursday.
“Environment Agency teams are out on the ground clearing grilles, screens and closing flood barriers.
“We urge people to keep away from swollen rivers and not to drive through flood water – it is often deeper than it looks and just 30cm of flowing water is enough to float your car.”
Met Office chief meteorologist Dan Suri said: “A low pressure system bringing severe weather to the UK this week has been named Storm Christoph.
“The rain will be heaviest on the western side of higher ground with over 100mm of rain expected quite widely and potentially up to 200mm possible in isolated, exposed areas.
“These rainfall totals, combined with melting snow across the hills, present a real threat of flooding.
“As well as heavy rain, strong winds and the potential for snow and ice will add to the unsettled, blustery feel to the weather especially in higher and more exposed locations.”