More than 13,000 homes are without power after Storm Imogen brought heavy rain and winds of up to 96mph to parts of southern Britain.
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.
BC 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.
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."
Problems so far include:
- Western Power Distribution says more than 13,000 homes are without power - more than 7,700 in the South West, more than 2,300 in Wales and more than 3,400 in the Midlands
- Ferry services from operators including P&O and Brittany are cancelled or delayed
- Drivers are being urged to take extra care, especially on the M4 and M5 motorways. The M48 Severn Bridge has been closed in both directions to high-sided vehicles because of high winds, although the M4 Second Severn Crossing remains open
- A number of schools in Cornwall are closed due to power cuts and storm damage
- Services are disrupted on a number of rail lines, including South West Trains,Arriva Trains Wales, Southern Railway and Great Western Railway. Speed restrictions are in place - for more information, go to National Rail Inquiries
- A train travelling from Penzance to Glasgow has crashed into a tree on the main line close to Bodmin Parkway station in Cornwall
- Gatwick Express services are suspended due to bad weather, and Gatwick Airport itself is also warning passengers their flights could be delayed
- A stretch of the A35 bypass at Dorchester has been closed by flooding
- The Emirates Air Line cable car across the River Thames is suspended due to high winds