Storm Eunice has claimed its first casualties in the UK, leaving three people dead.
One motorist died when a tree hit his car in Alton, East Hampshire, while a woman was also killed in similar circumstances in Haringey, London.
Another man, in his 50s, died when flying debris hit the windscreen of his vehicle in Liverpool.
Emergency services rushed to the scene of the first death in Alton after the tragic incident took place just before midday.
A white sheet this afternoon covered what is believed to be the battered vehicle, which was struck by a tree.
Meanwhile, a woman in her 30s was killed in Haringey when a tree fell on her car at roughly 4pm, with the male driver taken to hospital.
A 79-year-old man, from England, has also died in Belgium after being blown out of his boat during stormy conditions.
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The man fell into the water in the town of Leper, near the North Sea coast, and later died in hospital as a result of his injuries.
In Alton, branches were left scattered across the ground after a tree - thought to be 40ft tall - collapsed, killing the motorist.
An eyewitness, who is from Alton and didn't want to be named, said: "I was walking down the road when I came across the tree and I had to climb across it to get past it.
"At this point I couldn't see anything so I was just climbing.
"When I climbed over it I saw this white pick-up truck out of the corner of my eye.
"I thought to myself 'oh my Christ there is a car under there' and I looked and saw the man in the cab.
"The tree was across his cab, they were big, thick branches. The tree dented the vehicle, the roof of the cab was all dented in and the door was all dented in too.
"I could not believe it."
Photographs of a white Mercedes flat-bed van being recovered from the scene show devastating damage to its cab.
The trunk of the 'enormous' tree fell on the vehicle, thought to be white pick-up or flatbed van, according to the eyewitness.
A fire engine, two police cars and a JCB digger remained at the scene to begin work on removing the tree.
Emergency services workers wearing white overalls were attempting to remove at least one occupant of the vehicle.
Timothy Brant-Coles, who owns a self storage and removal business in Alton and was today working to remove trees from roads in the area, said he was 'on his way' to the incident earlier this afternoon which he heard was 'fatal'.
Meanwhile, the Mayor of London Sadiq Khan paid tribute to the woman who lost her life in Haringey today.
He said: "My thoughts and prayers are with the families of the woman who tragically lost her life and the man who was seriously injured in Highgate this afternoon.
"I’d like to pay tribute to all those in the emergency services who have been working tirelessly to keep us safe and urge all Londoners to remain cautious and avoid taking risks as this storm passes.”
A man in his 50s also died in Liverpool when flying debris hit his vehicle at around 2.10pm.
The driver of the vehicle was not injured.
The deaths in the UK come after a man in his 60s was killed by a falling tree in Ballythomas, Co Wexford, Ireland.
It is understood that the man was working with a colleague cleaning up tree debris when the tragedy struck.
Gardai are investigating the incident, the Irish Mirror reports.
Meanwhile, gusts of more than 100mph have hammered the UK and torn the roof off the O2 Arena in London.
Staff have described the terrifying moment the venue's roof was "ripped off" by Storm Eunice, saying there was a "huge whooshing" before everything was "completely exposed".
Huge gusts of wind ripped through the iconic venue's material roof, tearing two huge sections of it.
An employee told The Mirror they had been warned the venue, which contains dozens of bars and restaurants, a shopping centre and a massive live music venue, could be closed "for a few months".
London Fire Brigade has declared a major incident in the capital after being overwhelmed with calls.
It is now prioritising incidents which involve a 'risk to life' and urged people to avoid making 'unhelpful' 999 calls.
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The chaotic weather conditions have also led seven train operators to suspend services, with a rare "do not travel" alert issued for railways in England and Wales.
The following rail organisations have cancelled services due to Storm Eunice: c2c, Chiltern Railways, Great Western Railway, Greater Anglia, South Western Railway, Southeastern and Transport for Wales.
Network Rail closed all routes in Kent while every line in south-east London was blocked by trees.
South Western Railway said record-breaking winds had caused 'multiple incidents' - already downing 30 trees across routes.
In Monmouthshire highway crews have cleared more than 50 fallen trees which blocked roads.
The storm has also downed power lines throughout the country, leaving at least 27,000 properties without electricity in Cornwall.
