Britain is bracing for a second weekend of weather disruption, as experts warn Storm Dennis could inflict more damage than Ciara when it sweeps in later.
Severe weather warnings are in place for most of the UK - and forecasters say a month's worth of rain could fall in some places.
Road, rail and air travellers also face disruption, with British Airways and easyJet flights among those affected.
It comes after Storm Ciara flooded hundreds of homes last weekend.
The Environment Agency has warned flooding is likely to be worse this weekend as already saturated ground is met with a "perfect storm" of heavy rain, strong winds and melting snow.
are in place for most of the country from Saturday afternoon into Sunday evening.
This means flooding could cause a danger to life, power cuts are expected and there is a good chance transport links will be impacted.
EasyJet has confirmed the cancellation of 234 flights to, from and within the UK, while British Airways said it was making a "small number" of cancellations, merging some short-haul flights that are travelling to the same destination.
The LNER train company has already cancelled dozens of services between London and the north-east of England.
Other companies say services could be affected by speed restrictions as well as fallen trees and debris on the line.
It comes on a particularly busy weekend with many families having booked to travel over the half-term school holiday.
The worst-hit areas could see between 120-140mm of rainfall and gusts of up to 80mph over the weekend, the Met Office said.
The predictions are not as severe as last weekend when Ciara brought as much as 184mm of rain and gusts reaching 97mph, resulting in
But experts have warned Storm Dennis could cause more flooding damage, because of the heavy rain falling on parts of the UK still recovering from Ciara.
John Curtin, the Environment Agency's executive director of flood and coastal risk management, said Cumbria, Lancashire and Yorkshire were the areas he was most "concerned" about.
"This (storm) could be a step up from what we have seen before," Mr Curtin said.
"We had a big storm last weekend, (we now have) saturated catchments, snowmelt and rainfall, so it is a perfect storm."
The Environment Agency said preparations were under way to operate flood defences, flood storage reservoirs and temporary barriers to protect communities.
These include the Foss Barrier in York, the Thames Barrier in London and another in Bewdley, Worcestershire, on the River Severn.
UK power operators say they have employed extra engineers and call centre staff to respond to any possible impact of the storm, after widespread power cuts last weekend.
Newly-appointed Environment Secretary George Eustice said he had spoken to local flood response groups across the country on Friday.
Highlighting the Environment Agency's preparations, he added: "We are fully focused on ensuring that communities are protected and have access to the support and advice they need to stay safe this weekend."
Meanwhile, airlines have grounded flights in anticipation of the bad weather, and further cancellations may occur at short notice when the storm moves in on Saturday.
An easyJet spokesperson said: "We are doing everything possible to minimise the impact of the disruption for our customers and to arrange alternative travel.
"We will also provide hotel rooms and meals for customers who require them."
Network Rail is also advising passengers to expect delays and cancellations to services due to flooding, and to allow more time for their journeys.
Households living near rail lines have been asked to secure any loose gardens items, after several trampolines were blown on to the tracks last weekend.
At least 800 homes in the north of England and many other areas are at risk of being flooded over the weekend as Storm Dennis unleashes heavy rainfall.
That is the assessment of the Environment Agency which is warning that persistent intense rain will fall on ground already saturated.
Snow now lying on higher ground will be melted and will add to the threat.
The agency's head of flood defence, John Curtin, told a media briefing that 800 homes were flooded last weekend during Storm Ciara and that "my feeling is that this will be at least as bad, probably more so".
Over the course of the winter so far, 7% of 400 river gauges have set new records for water height.
Mr Curtin said temporary flood defences were being deployed in many places but added it was too early to tell exactly where the most intense rain would fall.
He said he was most concerned about Lancashire, Yorkshire and Cumbria but parts of Wales, south-west England, the Midlands and south-east England could also be at risk.
The Met Office has amber warnings for rain in pockets of northern and south-west England, and Wales from 12:00 GMT on Saturday until 15:00 on Sunday.
An amber warning is also in place for most of southern England from 00:15 until 18:00 on Sunday.
On Saturday morning, there were - meaning flooding is "expected" - and 141 flood alerts - meaning flooding is possible - in place across the country.
Yellow warnings for strong winds and heavy rain also cover all of England, Wales and southern Scotland between 09:00 GMT and midday on Saturday.
Further yellow warnings for wind are in place for northern parts of the UK from midday on Sunday until midday on Monday - potentially bringing travel disruption to commuters.