People are protecting their homes and businesses, roads have been closed and ferries cancelled as the UK prepares for the arrival of Storm Ciarán later.
Damaging winds are forecast in southern England and gusts of up to 95mph (152km/h) are predicted to batter the Channel Islands.
The Met Office has warned of travel disruption, damage to buildings and flying debris.
There are also 24 flood warnings in place across England.
It comes less than two weeks after Storm Babet wreaked havoc across the UK.
The Met Office has issued yellow and amber warnings - indicating potential risks to life and property - for wind and rain in southern and eastern England.
A red wind warning, the highest level, has been issued by Jersey Met for Wednesday night into Thursday, with storm-force gusts, heavy rainfall and coastal flooding.
From Wednesday, the East of England has yellow warnings for areas including central Essex, Suffolk, Norfolk, Southend-on-Sea and Hertfordshire.
Gusts of 70mph (112km/h) are possible on exposed parts of the south coast of England, with 20-30mm of rain expected in southern and western areas.
Storm Ciarán conditions on the Channel Islands are predicted to be the worst in more than 36 years. Main coastal roads on Jersey will be closed later and schools and the airport shut down on Thursday
Alerts for the Essex coast have been upgraded to amber from 06:00 GMT to 17:00 on Thursday
Southern Railway has urged commuters to work from home, warning it would be unlikely to provide rail replacement transport
The RAC has warned drivers in the south and west of the UK to avoid coastal and rural roads - where there is a greater chance of falling trees - and take care when passing high-sided vehicles.
People in Jersey and Guernsey have also been asked not to stockpile goods after supermarket shelves were stripped
Two hundred one-tonne bags of sand have been put at the top of slipways along the south coast of Jersey
Residents in Swindon have been handed more than 200 sandbags while council teams clear gullies and drains
Across England, 24 flood warnings have been issued as well as 116 flood alerts. Yellow rain warnings have been issued for eastern England, London, the South East, South West, North West, West Midlands and Wales from 18:00 on Wednesday.
Yellow warnings of wind have been issued for the East of England, London, South East, South West and Wales from 21:00 on Wednesday to 23:59 on Thursday.
In Scotland, a yellow warning of rain has been issued for parts of south west, central and eastern areas from 03:00 to 15:00 on Wednesday, and for the south west and Lothian Borders from 06:00 Thursday to 06:00 Friday. An earlier warning for rain in Northern Ireland has been cancelled.
East Devon District Council said a temporary barrier of sand and a fabric membrane were being put in place to reduce the impact of waves from the storm.
With trees still in full leaf and the ground already saturated, Devon County Council said there was a high chance that there would be a lot of debris on the roads and a risk of highway flooding.
It said it would have additional staff monitoring the highways, as well as tree surgeons and gully jetters on standby to keep drains and gullies as clear as possible.
Storm Ciarán follows localised weather-related incidents last weekend when large waves brought down coastal barriers in North Tyneside and homes were evacuated and shops were damaged when a village in County Durham was deluged by "several feet of water".
In West Sussex on Sunday, a caravan park in Bognor Regis was submerged, the town's Tesco supermarket car park was flooded, and the roof of a house was ripped off in heavy winds that residents described as like a "tornado".
