Storm Katie is set to batter Britain with 70 mile per hour winds and up to 1.4 inches of rain during a miserable Bank Holiday Monday.
Forecasters are warning of the possibility of falling trees and disruption to power supplies and travel amid a soggy end to Easter weekend.
The Met Office has issued a national weather warning for the eleventh storm to be named since last autumn.
A yellow severe warning for heavy, persistent rain and localised and surface-level flooding has been put in place for London and the South West for part of today.
And a separate yellow warning of high winds for London and the South East has also been issued, effect until 3pm today.
The heaviest rain is forecast to fall in central England, the South East, Lincolnshire and Yorkshire, with 10 to 15 millimetres in most areas and up to 35mms in others.
Meanwhile the wind could blow at speeds of up to 70mph in isolated areas across the South coast.
But by midday, the storm is set to move on and by 3pm it should have moved out to the North Sea.
The rest of the week looks to be showery for most parts of the country, with no sudden temperature rise despite the move into British Summer Time.
But Met forecasters say there is no reason to believe Katie is the last named storm, as this time of the year tends to be quite variable.
Frank Saunders, Chief Operational Meteorologist, said: "Southern England and south Wales will see very strong winds from the early hours of Monday morning.
"There is the potential for gusts of 50 to 60mph in inland areas. Exposed south and west-facing coasts could even see gusts of around 70mph, with the possibility of large waves.
"We expect the winds will start to ease in south-western Britain from mid morning, this improvement reaching other areas by late afternoon or early evening.
"There is currently some uncertainty about the track that Storm Katie will take, so we urge everyone, especially those travelling on Easter Monday, to look out for the latest information from the Met Office."
Met Office spokesperson Ellie Creed said: "While there is a national weather warning this will mainly affect the South.
"The storm is caused by low pressure developing and this will mainly affect South England and South Wales.
"It will start developing overnight tonight and will start coming the English channel and into South West England by early evening.
"By tomorrow morning the actual rain associated with the storm will be affecting central England, South East, Lincolnshire and Yorkshire.
"In terms of wind there will be strong winds affect the South West and South East and the Eastern side of East Anglia.
"You could see 50 to 60mph winds in these areas and across that Bristol Channel with some isolated areas seeing 70mph.
"The most persistent and heavy rain is likely to be in the South West and East Yorkshire with 10 to 15mms, but some isolated areas could see up to 35mm.
"The North will mainly avoid the rain.
"But although there will be a storm the temperature in the South Western part of the country will still be 12 to 13C. This is because under there we have still got a warm air mass.
"By midday the centre of the storm will be just off East Anglia coast and by 3pm it will effectively be in the North Sea.
"For the rest of the week it looks fairly showery with not much temperature change.
But despite this being the 11th storm to be named since last Autumn, Ms Creed said we could not count on Katie being the last.
Ms Creed added: "This time of the year tends to be quite variable."