In London, residents can expect outbreaks of heavy rain throughout the day.
Wind will also get stronger and the Met Office say there's the possibility of thunder at times.
It's a stark contrast to less than two weeks ago when the temperature reached 25C, but they're still getting off easily compared to a lot of the UK.
Stay away from water and cliffs, says RNLI
PA MediaCopyright: PA Media
The Royal National Lifeboat Institution (RNLI) has warned the public against going near cliff edges and the coast during the storm.
They say it "poses a safety risk to those visiting the coast".
Michael Avril, regional water safety lead Scotland, added: "It is a possibility that being too close to water and cliff edges in these conditions could knock you off your feet or wash you into the sea.
"It is not worth risking your life."
He advises the public to call 999 if they see someone in danger and ask for the Coastguard,
WATCH: Perth hoping for no repeat of Storm Agnes flooding
Video content
Video caption: 'Exceptional' levels of rainfall expected - BBC reporter'Exceptional' levels of rainfall expected - BBC reporter
BBC Scotland reporter Steven Godden is braving rain-lashed Perth to highlight flood prevention measures being put in place there.
It comes just weeks after the local authorities were heavily criticised for not closing flood gates quickly enough during Storm Agnes.
'More prepared for storm damage and the need for rest centres'
PA MediaCopyright: PA Media
Aberdeenshire Council has been reflecting on lessons learned from Storm Arwen in 2021 during a number resilience meetings, according to BBC reporter Neil Metcalf.
The council says it is more prepared than before, with people collecting sand bags and road teams clearing road gullies.
The council's chief executive Jim Savage tells BBC Scotland News there is "potential for rest centres as the storm proceeds" and he is pleading with residents to make sure they're prepared as well.
He says roads teams will be "out and about" clearing trees or drains.
What to expect as the day goes on
Video content
Video caption: The Met Office issues a rare red warning for rainThe Met Office issues a rare red warning for rain
As we edge closer to today's red warning for rain kicking in, Carol Kirkwood has all the latest details.
Share your experiences with us
BBCCopyright: BBC
How have you been affected by the strong winds and rain brought by Storm Babet? If it is safe to do so you can share your experiences, pictures and videos by emailing haveyoursay@bbc.co.uk.
Please read our terms & conditions and privacy policy. If you are willing to speak to a BBC journalist, please include a contact number.
How rare is a red weather warning?
These don't come around every day.
The last time the UK saw a red weather warning was in July last year, but that was for extreme heat.
Before that, the last red warning for rain was in February 2020 during Storm Dennis, affecting south Wales.
Scotland hasn't had a red rain warning since December 2015 over Storm Desmond.
High winds hit Scotland's west coast ferries
CalMacCopyright: CalMac
CalMac's Ullapool-Stornoway service is among those disrupted by the weatherImage caption: CalMac's Ullapool-Stornoway service is among those disrupted by the weather
Half of Caledonian MacBrayne's 29 ferry routes on Scotland's west coast have been disrupted by high winds.
There are suspensions, delays and cancellations in place on Thursday, with warnings of possible further disruption on Friday.
Affected routes include Ullapool-Stornoway, Oban-Castlebay and Ardrossan-Brodick.
Tall ship full of young carers forced to shelter from storm
Holly VintCopyright: Holly Vint
A ship run by a charity which gives young people the opportunity to volunteer on voyages has had to take shelter in Braehead on the River Clyde.
The volunteers - young carers aged between 11 and 16 - are on board the Alba Explorer which belongs to Ocean Youth Trust Scotland.
They have been on the ship since Monday and were supposed to sail around the Isle of Arran and surrounding areas, but last night skipper Holly Vint decided to dock on the Clyde after news of the storm.
She said despite the change in plans the young carers have not been too disappointed.
Holly VintCopyright: Holly Vint
"I think they are quite enjoying this morning being tucked down below warm and dry given how horrible it is on deck right now," she told BBC's Good Morning Scotland.
“It’s pretty gusty and actually last night, even though we are in really sheltered waters here, quite a few of us were woken up at various points with the gusts heeling the boat over, so we're very glad to be here and not out at anchor somewhere.
The trip was supposed to last until Friday but the skipper said it will probably have to be cut short.
"There's a little window in the afternoon where we might be able to get back to Greenock which is our home dock. They (the young carers) might have to go home a bit earlier," she said.
'Storm Babet caught us off guard - we've lost everything'
BBCCopyright: BBC
A shipping container belonging to a beach bar in Torquay was washed into the seaImage caption: A shipping container belonging to a beach bar in Torquay was washed into the sea
Southern parts of the UK have already felt the effects of Storm Babet as the weather front swept its way north and east.
In Devon, Sean White says his Torquay beach bar was destroyed during high tide on Tuesday.
He says a storm surge "caught us off guard", adding: "We’re devastated... we've lost everything."
Major damage was also done to a number of beach huts in Paignton and Teignmouth.
Video caption: The Met Office issues a rare red warning for torrential rainThe Met Office issues a rare red warning for torrential rain
As we have been reporting, red warnings from the Met Office are only issued in the most extreme weather and are therefore rare.
It represents a "risk to life" alert during Storm Babet, with predicted rainfall and subsequent flooding being described as exceptional.
Tomasz Schafernaker has the details.
What storm names are on this year's list?
.Copyright: .
Storm Agnes, which was recognised as the first storm of the season, was named after Agnes Mary Clerke, an Irish astronomer and science writer.
Storm Babet - a name selected by the Dutch weather agency KMNI - was named after a woman who visited an open day at its headquarters and put her own name forward, with the additional reason "because I was born during a storm".
By the way, if you are wondering, its Dutch origin means the storm name is pronounced Bab-ET (with the stress on the second syllable), rather than Bab-AY, according to the BBC Pronunciation Unit.
The third storm of the year will be named after Ciarán Fearon, who works in the Department for Infrastructure in Northern Ireland.
If we get as far as 10 storms this year, then Dame Jocelyn Bell-Burnell, a leading astrophysicist from Northern Ireland, will have provided the inspiration although she said: "Hopefully they won't get that far."
How Storm Babet and other UK storms get their names
ReutersCopyright: Reuters
The UK Met Office and Irish service Met Éireann launched their first "Name our Storms" campaign in 2015.
Most years, they draw the names from a shortlist of favourites submitted by the public. And since 2019, they have been joined by the national weather service of the Netherlands which also chips in a few suggested names each year.
For the 2023/24 season, the Met Office has slightly changed its methods and has named a number of storms after prominent scientists, meteorologists and, in its words, others "who work to keep people safe in times of severe weather".
In the past, storms have alternated between male and female names but that has altered this year in order to honour the right people.
How bad could it get?
So just how heavy could the rainfall be?
Well, between 10-15cm (4-6in) of rain expected to fall quite widely within the warning period and some locations in Angus and Aberdeenshire are likely to see between 20-25cm (8-10in).
It has been described by the Scottish Environment Protection Agency (Sepa) as "unprecedented".
The flood gates have closed as Perth braces itself
Steven Godden
BBC Scotland News
BBCCopyright: BBC
Here in the Perth, the impact of Storm Agnes at the end of September is fresh in
people’s minds
Those in the water-damaged properties close to the River
Tay were angry the city’s flood gates weren’t closed in time.
And so this morning those metal barriers are firmly
closed and will stay shut as people wait for the worst of the weather to pass.
Standing by the river, it was windy but still dry when the amber rain warning came into effect at six o’clock.
But conditions quickly worsened for the hardy joggers and
early-morning dog walkers passing by.
As conditions deteriorate, people in the amber zones are
being advised not to travel unless absolutely necessary.
How will Babet affect the rest of the UK?
Scotland looks like it will take the brunt of Storm Babet, but huge swathes of the rest of the UK will also be badly hit.
Parts of Northern Ireland and northern and eastern England already saturated from recent floods will see strong winds and heavy rain on Thursday.
Yellow severe weather warnings have been issued through to Saturday.
In Northern Ireland, the yellow rain warning which has been in place since 14:00 BST on Wednesday is set to last until 10:00 BST on Thursday.
'Lessons have been learned from Storm Arwen'
SSENCopyright: SSEN
A damaged powerline in Aberdeenshire during Storm ArwenImage caption: A damaged powerline in Aberdeenshire during Storm Arwen
Power firm SSEN says 2021's Storm Arwen has helped shape its preparations for the latest forecasted bad weather.
Thousands of homes were left without electricity - some for several days - after Arwen's 100mph winds blasted the north east of Scotland, Dumfries and Galloway and Scottish Borders
SSEN's Graeme Keddie tells the BBC's Good Morning Scotland Storm Babet is not expected to bring the same level of impact, but warns Aberdeenshire and Angus could see gusts of up to 70mph.
"We have invested in our network since Storm Arwen," he says.
The actions taken include removing trees near powerlines, burying some stretches of cable underground and adding additional generator hook up points.
The company says staff numbers in its contact centres are also increased during stormy weather.
Transport problems: The story so far
If you are just joining us, there has already been major disruption on the transport network as Storm Babet starts to roll across Scotland.
ScotRail has cancelled the following services:
Perth-Aberdeen via Dundee, Perth-Aviemore (Highland main line), Perth-Dunblane, Aberdeen-Elgin (Aberdeen- Inverness line), Tain-Wick/Thurso (Far North line), and Fife Circle services.
The cancellations will also affect services between Glasgow Queen Street and Aberdeen and Inverness, and between Edinburgh Waverley and Aberdeen and Inverness.
The Forth Road Bridge has been closed.
NorthLink ferries have cancelled sailings today between Aberdeen and Orkney and Shetland.
Pentland and Orkney ferries have also said there will be no sailings today and into Friday.
CalMac ferries are at "heightened risk of disruption".
The latest weather update from the BBC's Simon King
Simon King
BBC weather presenter and meteorologist
Rain will be moving into eastern Scotland this morning where
there’s an amber warning in force. Winds will also be picking up in the
north and east with gusts in excess of 70mph for some.
With the rain turning increasingly heavy in Angus and parts
of Aberdeenshire, significant impacts from flash and river flooding will start
to be seen later with the rare red warning in force from 6pm.
Why has a red warning been issued?
Red warnings from the Met Office are only issued in the most
extreme weather and are therefore rare. The last red warning for rain was
during Storm Dennis in 2020, for example.
With over two months worth of rain falling (around 200mm) in two days across eastern Scotland, there’ll be extensive flash and river flooding.
The advice from emergency services is to stay at home unless told otherwise.
No replacement transport for cancelled ScotRail services
BBCCopyright: BBC
ScotRail service delivery director, David Simpson, tells BBC Radio's Good Morning Scotland programme there is no replacement transport for cancelled services.
The affected routes are Perth-Aberdeen via Dundee, Perth-Aviemore (Highland main line), Perth-Dunblane, Aberdeen-Elgin (Aberdeen- Inverness line), Tain-Wick/Thurso (Far North line), and Fife Circle services.
The cancellations will also affect services between Glasgow Queen Street and Aberdeen and Inverness, and between Edinburgh Waverley and Aberdeen and Inverness.
Travellers on other services are being encouraged to check the ScotRail website and app before they set off.
If you have bought a ticket for a cancelled train, you can get a free refund or use your ticket when services get back to normal.
Live Reporting
Edited by Paul McLaren and Mary McCool
All times stated are UK
Get involved
London braced for heavier rain and strong winds
In London, residents can expect outbreaks of heavy rain throughout the day.
Wind will also get stronger and the Met Office say there's the possibility of thunder at times.
It's a stark contrast to less than two weeks ago when the temperature reached 25C, but they're still getting off easily compared to a lot of the UK.
Stay away from water and cliffs, says RNLI
The Royal National Lifeboat Institution (RNLI) has warned the public against going near cliff edges and the coast during the storm.
They say it "poses a safety risk to those visiting the coast".
Michael Avril, regional water safety lead Scotland, added: "It is a possibility that being too close to water and cliff edges in these conditions could knock you off your feet or wash you into the sea.
"It is not worth risking your life."
He advises the public to call 999 if they see someone in danger and ask for the Coastguard,
WATCH: Perth hoping for no repeat of Storm Agnes flooding
Video content
BBC Scotland reporter Steven Godden is braving rain-lashed Perth to highlight flood prevention measures being put in place there.
It comes just weeks after the local authorities were heavily criticised for not closing flood gates quickly enough during Storm Agnes.
'More prepared for storm damage and the need for rest centres'
Aberdeenshire Council has been reflecting on lessons learned from Storm Arwen in 2021 during a number resilience meetings, according to BBC reporter Neil Metcalf.
The council says it is more prepared than before, with people collecting sand bags and road teams clearing road gullies.
The council's chief executive Jim Savage tells BBC Scotland News there is "potential for rest centres as the storm proceeds" and he is pleading with residents to make sure they're prepared as well.
He says roads teams will be "out and about" clearing trees or drains.
What to expect as the day goes on
Video content
As we edge closer to today's red warning for rain kicking in, Carol Kirkwood has all the latest details.
Share your experiences with us
How have you been affected by the strong winds and rain brought by Storm Babet? If it is safe to do so you can share your experiences, pictures and videos by emailing haveyoursay@bbc.co.uk.
You can also get in touch in the following ways:
Please read our terms & conditions and privacy policy. If you are willing to speak to a BBC journalist, please include a contact number.
How rare is a red weather warning?
These don't come around every day.
The last time the UK saw a red weather warning was in July last year, but that was for extreme heat.
Before that, the last red warning for rain was in February 2020 during Storm Dennis, affecting south Wales.
Scotland hasn't had a red rain warning since December 2015 over Storm Desmond.
High winds hit Scotland's west coast ferries
Half of Caledonian MacBrayne's 29 ferry routes on Scotland's west coast have been disrupted by high winds.
There are suspensions, delays and cancellations in place on Thursday, with warnings of possible further disruption on Friday.
Affected routes include Ullapool-Stornoway, Oban-Castlebay and Ardrossan-Brodick.
Tall ship full of young carers forced to shelter from storm
A ship run by a charity which gives young people the opportunity to volunteer on voyages has had to take shelter in Braehead on the River Clyde.
The volunteers - young carers aged between 11 and 16 - are on board the Alba Explorer which belongs to Ocean Youth Trust Scotland.
They have been on the ship since Monday and were supposed to sail around the Isle of Arran and surrounding areas, but last night skipper Holly Vint decided to dock on the Clyde after news of the storm.
She said despite the change in plans the young carers have not been too disappointed.
"I think they are quite enjoying this morning being tucked down below warm and dry given how horrible it is on deck right now," she told BBC's Good Morning Scotland.
“It’s pretty gusty and actually last night, even though we are in really sheltered waters here, quite a few of us were woken up at various points with the gusts heeling the boat over, so we're very glad to be here and not out at anchor somewhere.
The trip was supposed to last until Friday but the skipper said it will probably have to be cut short.
"There's a little window in the afternoon where we might be able to get back to Greenock which is our home dock. They (the young carers) might have to go home a bit earlier," she said.
'Storm Babet caught us off guard - we've lost everything'
Southern parts of the UK have already felt the effects of Storm Babet as the weather front swept its way north and east.
In Devon, Sean White says his Torquay beach bar was destroyed during high tide on Tuesday.
He says a storm surge "caught us off guard", adding: "We’re devastated... we've lost everything."
Major damage was also done to a number of beach huts in Paignton and Teignmouth.
Read more here
Take it as red - this is extreme weather
Video content
As we have been reporting, red warnings from the Met Office are only issued in the most extreme weather and are therefore rare.
It represents a "risk to life" alert during Storm Babet, with predicted rainfall and subsequent flooding being described as exceptional.
Tomasz Schafernaker has the details.
What storm names are on this year's list?
Storm Agnes, which was recognised as the first storm of the season, was named after Agnes Mary Clerke, an Irish astronomer and science writer.
Storm Babet - a name selected by the Dutch weather agency KMNI - was named after a woman who visited an open day at its headquarters and put her own name forward, with the additional reason "because I was born during a storm".
By the way, if you are wondering, its Dutch origin means the storm name is pronounced Bab-ET (with the stress on the second syllable), rather than Bab-AY, according to the BBC Pronunciation Unit.
The third storm of the year will be named after Ciarán Fearon, who works in the Department for Infrastructure in Northern Ireland.
If we get as far as 10 storms this year, then Dame Jocelyn Bell-Burnell, a leading astrophysicist from Northern Ireland, will have provided the inspiration although she said: "Hopefully they won't get that far."
How Storm Babet and other UK storms get their names
The UK Met Office and Irish service Met Éireann launched their first "Name our Storms" campaign in 2015.
Most years, they draw the names from a shortlist of favourites submitted by the public. And since 2019, they have been joined by the national weather service of the Netherlands which also chips in a few suggested names each year.
For the 2023/24 season, the Met Office has slightly changed its methods and has named a number of storms after prominent scientists, meteorologists and, in its words, others "who work to keep people safe in times of severe weather".
In the past, storms have alternated between male and female names but that has altered this year in order to honour the right people.
How bad could it get?
So just how heavy could the rainfall be?
Well, between 10-15cm (4-6in) of rain expected to fall quite widely within the warning period and some locations in Angus and Aberdeenshire are likely to see between 20-25cm (8-10in).
It has been described by the Scottish Environment Protection Agency (Sepa) as "unprecedented".
The flood gates have closed as Perth braces itself
Steven Godden
BBC Scotland News
Here in the Perth, the impact of Storm Agnes at the end of September is fresh in people’s minds
Those in the water-damaged properties close to the River Tay were angry the city’s flood gates weren’t closed in time.
And so this morning those metal barriers are firmly closed and will stay shut as people wait for the worst of the weather to pass.
Standing by the river, it was windy but still dry when the amber rain warning came into effect at six o’clock.
But conditions quickly worsened for the hardy joggers and early-morning dog walkers passing by.
As conditions deteriorate, people in the amber zones are being advised not to travel unless absolutely necessary.
How will Babet affect the rest of the UK?
Scotland looks like it will take the brunt of Storm Babet, but huge swathes of the rest of the UK will also be badly hit.
Parts of Northern Ireland and northern and eastern England already saturated from recent floods will see strong winds and heavy rain on Thursday.
Yellow severe weather warnings have been issued through to Saturday.
In Northern Ireland, the yellow rain warning which has been in place since 14:00 BST on Wednesday is set to last until 10:00 BST on Thursday.
'Lessons have been learned from Storm Arwen'
Power firm SSEN says 2021's Storm Arwen has helped shape its preparations for the latest forecasted bad weather.
Thousands of homes were left without electricity - some for several days - after Arwen's 100mph winds blasted the north east of Scotland, Dumfries and Galloway and Scottish Borders
SSEN's Graeme Keddie tells the BBC's Good Morning Scotland Storm Babet is not expected to bring the same level of impact, but warns Aberdeenshire and Angus could see gusts of up to 70mph.
"We have invested in our network since Storm Arwen," he says.
The actions taken include removing trees near powerlines, burying some stretches of cable underground and adding additional generator hook up points.
The company says staff numbers in its contact centres are also increased during stormy weather.
Transport problems: The story so far
If you are just joining us, there has already been major disruption on the transport network as Storm Babet starts to roll across Scotland.
ScotRail has cancelled the following services:
Perth-Aberdeen via Dundee, Perth-Aviemore (Highland main line), Perth-Dunblane, Aberdeen-Elgin (Aberdeen- Inverness line), Tain-Wick/Thurso (Far North line), and Fife Circle services.
The cancellations will also affect services between Glasgow Queen Street and Aberdeen and Inverness, and between Edinburgh Waverley and Aberdeen and Inverness.
The Forth Road Bridge has been closed.
NorthLink ferries have cancelled sailings today between Aberdeen and Orkney and Shetland.
Pentland and Orkney ferries have also said there will be no sailings today and into Friday.
CalMac ferries are at "heightened risk of disruption".
The latest weather update from the BBC's Simon King
Simon King
BBC weather presenter and meteorologist
Rain will be moving into eastern Scotland this morning where there’s an amber warning in force. Winds will also be picking up in the north and east with gusts in excess of 70mph for some.
With the rain turning increasingly heavy in Angus and parts of Aberdeenshire, significant impacts from flash and river flooding will start to be seen later with the rare red warning in force from 6pm.
Why has a red warning been issued?
Red warnings from the Met Office are only issued in the most extreme weather and are therefore rare. The last red warning for rain was during Storm Dennis in 2020, for example.
With over two months worth of rain falling (around 200mm) in two days across eastern Scotland, there’ll be extensive flash and river flooding.
The advice from emergency services is to stay at home unless told otherwise.
No replacement transport for cancelled ScotRail services
ScotRail service delivery director, David Simpson, tells BBC Radio's Good Morning Scotland programme there is no replacement transport for cancelled services.
The affected routes are Perth-Aberdeen via Dundee, Perth-Aviemore (Highland main line), Perth-Dunblane, Aberdeen-Elgin (Aberdeen- Inverness line), Tain-Wick/Thurso (Far North line), and Fife Circle services.
The cancellations will also affect services between Glasgow Queen Street and Aberdeen and Inverness, and between Edinburgh Waverley and Aberdeen and Inverness.
Travellers on other services are being encouraged to check the ScotRail website and app before they set off.
If you have bought a ticket for a cancelled train, you can get a free refund or use your ticket when services get back to normal.