The Met Office has heightened weather warnings across the UK due to the risk of flooding posed by Storm Dennis.
The fourth named storm of the 2019-2020 season will hit the country from Saturday morning, bringing strong winds and heavy rain.
A total of three new amber warnings covering areas of high land and associated rivers have been issued for a 24-hour period over the weekend.
Forecasters predict “very heavy rain” will strike areas around the Brecon Beacons in South Wales, the Yorkshire Dales and Dartmoor in Devon from 3pm on Saturday to 3pm on Sunday.
On Sunday, a fourth amber warning for areas south of London, stretching from Andover in Hampshire eastwards, has also been issued from shortly after midnight until 6pm.
Conditions are likely to bring flooding to homes and businesses, causing damage to some buildings, the Met Office warned.
Fast flowing or deep floodwater is also likely, “causing danger to life”, while trains, buses and roads could be hit by closures, cancellations and delays.
There is a risk of communities being cut off by flooded roads and power cuts in affected areas.
Three large yellow warnings for strong winds and heavy rain also cover all of England, Wales and southern Scotland from between 9am and midday on Saturday.
The rain and wind is expected to track east throughout the weekend, with the warnings for England and Wales lasting until late on Sunday night.
The wind warning over Scotland will grow on Sunday to encompass the whole region, including Northern Ireland, persisting until midday on Monday.
The arrival of Storm Dennis comes just a week after Storm Ciara battered parts of the country, bringing winds of up to 97mph.
Met Office meteorologist Matthew Box said inland gusts could reach 50mph by Saturday afternoon, rising to 80mph in exposed areas in the south and west.
He said: “The winds will be a touch down on what we saw with Ciara but the focus is on a bit more rain with Storm Dennis due to the persistence of the rain.”
Higher locations could have rainfall levels of 50mm to 80mm over the course of the weekend, potentially rising to 140mm in some parts, Mr Box said.
More widely, rain totals could be around 20mm to 40mm, with the Environment Agency urging people to check for flood warnings.
It said preparations were under way to operate flood defences, flood storage reservoirs and to put up temporary barriers to protect communities.
This includes the Foss Barrier in York, the Thames Barrier in London and another in Bewdley, Worcestershire, on the River Severn.
With Storm Dennis on its way we want to remind you not to drive through flood waterâ ï¸— Env Agency Midlands (@EnvAgencyMids) February 12, 2020
Just 30cm of flowing water is enough to move your car. Make sure you are signed up to our flood warning service: https://t.co/4HSc5MbL20#flood #safety pic.twitter.com/A5Olv6kWC2
Caroline Douglass, flood duty manager at the Environment Agency, said: “Remember to never drive or walk through floodwater, just 30cm of flowing water is enough to move your car – it’s not worth the risk.”
Mr Box said the start of half term for some children this weekend means families should plan ahead or consider delaying their travels.
He warned rain could help topple sodden trees, affecting power lines, while strong winds could affect transport links such as ferries.
The AA has urged the public to follow safety advice on the roads, with Ben Sheridan, AA patrol of the year, saying: “Take extra care when passing high-sided vehicles, cyclists and motorbikes, and watch out for sudden gusts, which can blow debris, trees and even damaged vehicles into your path.”