Forecasters say Eunice, the UK's second storm in a week, could be one of the worst in three decades. Gusts have already exceeded 100mph in places.
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Porthcawl, Bridgend (above and below)
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People are being urged to avoid travelling if they can and stay at home when winds reach top speeds.
The Met Office issued red warnings for south Wales and the northern coast of south-west England until 12:00.
A second red warning for wind - the highest level - covers London, the South East and parts of the South and East of England from 10:00 GMT until 15:00.
Meanwhile, yellow warnings for snow and wind are also in place in Northern Ireland, northern England and parts of Scotland.
Here are pictures from across the UK showing wind, snow and disruption.
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Damage to the roof of the O2 Arena in south-east London (above and below)
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Brighton, East Sussex
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Clevedon, Somerset
BBC
A still from a video showing the top section of the spire at St Thomas's Church in Wells, Somerset, falling. The Grade II-listed church was built in the 1850s
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Porthcawl, Bridgend
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The roof of a building blown on to railway tracks in Banbury, Oxfordshire
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Aberystwyth promenade (above and below)
Alamy Live News
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Two cars crushed under a fallen tree in the village of Walditch, just outside Bridport, Dorset
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A fallen tree in Bude, Cornwall
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A lorry blown over on the M4 in Margam, Neath Port Talbot
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A fallen branch on a car in a car park in Lyme Regis, Dorset
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Council workers and members of the public attempt to clear a fallen tree from the A394 road near Penzance, Cornwall
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Edinburgh Castle
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Paisley, Renfrewshire
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Lyme Regis, Dorset
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A coastguard search-and-rescue team asks a swimmer to come out of the sea in New Brighton, Merseyside