More than 13,000 homes are without power after Storm Imogen brought heavy rain and winds of up to 96mph to parts of southern
South-west England, south and mid-Wales and the Midlands have borne the brunt so far, with eastern areas set to be hit later.
The strongest gust was recorded at The Needles off the Isle of Wight.
Rail services are disrupted, some cross-Channel ferries are cancelled and drivers are urged to take extra care.
The Met Office has issued an amber "be prepared" wind warning for Wales, south-west England, London and south-east England and
says coastal areas could see giant waves and localised flooding.
BBC Weather forecaster Peter Sloss said there had not been winds so strong across such a wide area of southern Britain since the
winter of 2013-14.
Winds of 70-80mph have been recorded in many areas, including 78mph in the Isles of Scilly and 74mph in Mumbles, near Swansea.
The sea state could reach "phenomenal" - the highest level on the World Meteorological Scale - at times around western coasts, with
waves of more than 14m (46ft) forecast.
Latest live updates from south-west England as Storm Imogen hits
There are nearly 60 flood warnings in place in England and Wales - meaning flooding is expected - and more than 200 flood alerts -
meaning flooding is possible.
Met Office forecaster Craig Snell said: "People should be prepared for disruption to travel on roads, rail, bridges and ferries and we
could see possible damage to structures and downed trees risk affecting power.
"The wind will be combined with some hefty showers with some thunder along the south coast."
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