Storm Dennis could flood hundreds of homes across the UK this weekend, as the Met Office issued danger to life warnings for parts of the country.
The UK is also bracing for more transport disruption as the perfect storm approaches, bringing gusts of up to 70mph (113kmph).
Some parts of the country could see up to 120mm (4.7in) of rain.
Power cuts are also expected and there is a good chance train and buses will see cancellations or delays and roads closed.
The Met Office says Storm Dennis poses a greater risk of widespread flooding than Storm Ciara the weekend before.
The Environment Agency (EA) said this is due to rain falling on already saturated ground.
Forecasters have issued eight weather warnings covering most of the UK.
This includes amber warnings from midday on Saturday over southern Scotland, northern England, Wales and part of the South West saying that flooding could cause a danger to life.
The storm could bring a month’s rain in one day.
More widely, yellow warnings the length and breadth of the UK are alerting the public to strong winds and rain as early as 7am in Scotland on Saturday, with regions further south feeling the impact from around 10am or midday.
The Met Office said the main areas of concern on Saturday are north and southwest England and Wales, with the South East bearing the brunt more on Sunday.
Flood defences are due to be in operation this weekend, with additional temporary flood barriers being installed in Shropshire, Lancashire, Yorkshire and Surrey.
More than 500 staff are on active incident duty and 30 mobile pumps have been deployed, the EA said.
Network Rail has advised passengers to expect disruption on many routes due to flooding and to allow more time for their journeys.
Meanwhile, people living near rail lines are being urged to secure any loose items in their gardens, after several trampolines were blown on to tracks and overhead electric wires last weekend, blocking lines.
The storm is also likely to cause treacherous driving conditions, with drivers urged not to attempt entering deep floodwater.
Storm Ciara left 800 properties flooded in England alone, according to the EA.
The Met Office has said that 82% of the UK’s average month’s worth of rainfall fell between 1 and 13 February this month.
Northern Ireland had 114% of its rainfall for the same period.
John Curtin, the agency’s executive director of flood and coastal risk management, said Storm Dennis could be a perfect storm and a step up from what we have seen before.
Newly-appointed Environment Secretary George Eustice said authorities were fully focused on ensuring that communities are protected.
There will be a heightened risk of flooding in parts of West and North Yorkshire, Lancashire and Greater Manchester, Hampshire, Sussex, Surrey and Kent.
As of 9.30pm on Friday, there were 12 flood warnings – meaning flooding is expected – and 141 flood alerts, which means flooding is possible.
Delays and cancellations to transport are also expected, with Network Rail warning that tracks in the North West could be particularly at risk due to the ground being waterlogged since last week.
Driving conditions are also expected to be treacherous as the rain will significantly reduce visibility, according to the AA.