The third named storm of the season could bring up to 50mm (two inches) of rain to parts of southern England today - just days after Storm Bert brought torrential rain and major disruption over the weekend.
The Dutch weather service KNMI named the new storm, Conall, as it headed towards the south of England bringing an area of low pressure.
After heavy rain in southern counties, it will deepen further to bring strong winds across the Netherlands later on Wednesday and into Thursday.
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A Met Office yellow rain warning has been issued for southern England, including Kent, Sussex and the Isle of Wight, and a small area around Plymouth in Devon from 10pm on Tuesday to midday on Wednesday.
Essex, Surrey, Hampshire, Dorset, and parts of London will also be affected.
Between 15 and 20mm (0.6-0.8 of an inch) of rain is likely with 30-40mm (1.2-1.6 of an inch) in some areas and a lower chance of 50mm in parts of the South East, with some travel disruption and flooding of "a few homes and businesses" expected, the Met Office said.
It comes as communities are still clearing up after Storm Bert, which brought torrential rain and winds of more than 80mph, turning roads into rivers and flooding hundreds of homes.
Earlier, the Met Office warned more flooding is "likely" to hit the UK this week, with further potentially heavy rain arriving across southern areas alongside colder temperatures on Wednesday.
Chris Wilding, of the Environment Agency, said "significant flooding impacts" are probable in parts of Northamptonshire, with "minor" flooding on the River Severn.
Flooding impacts are not expected to worsen in Yorkshire and the West Midlands over the next few days.
Additional minor river and surface water flooding impacts are also "probable" in parts of the south and east of England from late on Tuesday and through Wednesday, Mr Wilding said.
There were more than 90 flood warnings and more than 120 flood alerts still issued across the UK as of Tuesday evening.
A severe flood warning, meaning there is danger to life, was still in place in Billing Aquadrome holiday park and the surrounding parks next to the River Nene in Northampton.
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The naming of storms is shared by the KNMI, the Met Office and Ireland's Met Eireann to make communication of severe weather easier.
The storms list - first launched in 2015 - for each year generally runs from early September until late August the following year, coinciding with the beginning of autumn.
(c) Sky News 2024: Storm Conall: Third storm of the season to bring heavy rain to the South tonight