Wirral has been upgraded to an AMBER weather warning for heavy rain through the weekend.
Heavy rain could bring danger to life flooding, damage to buildings and transport disruption.
The rain is set to last from 12 pm Saturday to 3 am Sunday, bringing up to 25-90 mm of rain.
Steve Ramsdale, Chief Meteorologist at the Met Office, said: “It’ll be quite a miserable end to the working week for southern and south-west England as Storm Alex brings heavy rain and strong winds tomorrow, with coastal gales of around 60-65mph for some.
“Away from the south it’ll be a more pleasant day, with light winds and bright spells for much of northern England, Scotland and Northern Ireland.
“However, as the strong winds and rain associated with Storm Alex clear away from Britain later on Friday, another low-pressure system moves towards the UK from the east bringing further very heavy rain and strong winds to many over the weekend.”
Deputy Chief Meteorologist at the Met Office, Nick Silkstone, said: “Saturday will be a very wet day as heavy bands of rain push north and west across the country, followed by showery rain on Sunday.
“It’ll be cold and windy too with a risk of coastal gales in some areas. The Met Office has issued a rain warning covering large parts of the country over the weekend and we’re urging people to keep a close eye on the weather forecast and warnings during this spell of disruptive weather.”
Heavy rain could to lead to significant impacts from flooding, an enhanced risk of landslides along with very difficult driving conditions.
Jonathan Day, Flood Duty Manager at the Environment Agency, said: “Heavy rain will bring the potential for surface water flooding and perhaps some river flooding across the south of England on Friday.
“More widespread and persistent heavy rain across much of England will bring the potential for further river and surface water flooding over the weekend.
“Environment Agency teams have been working hard to clear grills and weed screens in areas which may be affected, and are ready to support local authorities leading on responses to surface water flooding incidents, should they occur.
“We urge people to stay away from swollen rivers and not to drive though flood water – it is often deeper than it looks and just 30cm of flowing water is enough to float your car. “