The Met Office has upgraded the weather warning for Storm Ciarán on Thursday to amber, saying winds may exceed 85mph in exposed coastal areas.
A yellow warning for rain is also in place, with up to 6cm possible on higher ground.
Large waves are expected to batter the south coast.
The wind warning says: “On Thursday morning very strong west to southwesterly winds will develop over parts of the far south and southeast of England where gusts are likely to reach 70-80 mph in some coastal areas and may exceed 85 mph in a few of the most exposed English Channel coastal spots.
“The extent of these high winds remains a little uncertain and is dependent on the exact track of Storm Ciarán. Winds will begin to ease from the west during the afternoon.
“Very large waves could bring additional impacts to coastal areas, especially along the English Channel coastline.”
The rain warning says: “Periods of heavy rain, associated with Storm Ciarán, are expected to affect much of southern Britain from Wednesday evening and during Thursday.
“A further 20 to 30 mm is likely quite widely, but 40-60 mm may accumulate in places, especially, but not exclusively, over higher ground.
“Given this amount of rainfall, the current saturated conditions, and the potential for fallen leaves to block drains etc – further impacts are likely.”
