Northern Ireland, north Wales and north-west England are being pounded by gales and heavy rain in the second band of storms to hit the UK in three days.
The storm blew the roof off a building in Greater Manchester
Forecasters say gusts of up to 80mph have hit Northern Ireland as the Atlantic weather front moves eastwards.
Motorists faced chaos as several major bridges were affected by the gales and some areas were placed on flood alert.
The second day of the prestigious Cheltenham horse racing festival has been abandoned because of the weather.
The course is in good condition but fierce winds made the huge marquees in the tented hospitality area unsafe.
The 55,000 people expected to attend the day's racing will get a full refund and the course is considering increasing its capacity for the rest of the week.
Cheltenham managing director Edward Gillespie said Wednesday's races would be run over the remaining two days of the festival.
In Cheshire, the M6 Thelwall Viaduct closed after three lorries overturned but there were no casualties.
The vehicles have been cleared but the eight-lane stretch of the motorway spanning the Mersey and the Manchester ship canal is still closed at Thelwall because of the danger from high winds.
There are two-mile tailbacks in both directions but traffic was reported as moving slowly as far south as Knutsford, about seven miles away.
High-sided vehicles are being advised against using the A533 Runcorn-Widnes bridge.
The Humber Bridge is shut to high-sided vehicles and has a 30mph speed limit for all other vehicles.
Some 750 homes have been left without power in Northern Ireland, and gusts of 85mph have been recorded in north Wales
A tree fell on to a coach in high winds on the A26 near Uckfield in East Sussex at 0735 GMT.
Sussex Police said the vehicle was empty apart from the driver, and no one was injured.
Police closed a road in Carrington, Greater Manchester, to protect the public after winds ripped off part of the roof of a council depot building.
Rail passengers have been advised to avoid travelling on the East Coast Mainline.
Network Rail has an 80mph speed limit in place between Stevenage and Berwick-upon-Tweed because of the risk of track obstruction or power line failure.
Train operator National Express East Coast said the limit would be reviewed throughout the day, and was hopeful the London to Edinburgh journey time would return to the normal four-and-a-half hours on Thursday.
There are two-hour delays between Dover and Calais on P&O ferries, and services across the Irish Sea are also affected.
Ian Jackson, from Liverpool coastguard, said the storms were likely to continue in the North West for most of the day.
He said: "The forecast is for the wind to decrease to force five, then perhaps come up again to force seven later on today."
Steve Crosthwaite, of the Highways Agency, is tracking the progress of the storm.
He said: "The winds will start to abate as the morning goes on but it will be very slow.
"But as the winds go over the Pennines, round about late morning and early afternoon, the eastern side of the country will start getting hit as well."
The Met Office has warnings of severe gales for all of the UK except northern Scotland and southern England.
By early afternoon the Environment Agency had one flood warning and 11 flood watches in place, with an "all clear" given for 55 locations which had previously been under threat.
BBC weather forecasters say a low pressure front could even bring snow to higher ground in parts of northern England and southern Scotland.
Later on Wednesday, the storms will move across central northern England and East Anglia.
Areas further south, which are still clearing up after Monday's storms, escaped the worst of the weather this time.
The Energy Networks Association said of the 30,000 people who lost power in those storms just "a few hundred" in the east of England were still without supply.