A yellow weather warning for wind was issued for the whole of England and Wales, with winds of up to 60mph forecast to batter the Midlands.
The alert, which says wind speeds could reach 70mph in coastal areas, was in force from 3pm on Boxing Day.
In addition to the strong winds, the Met Office forecast heavy rain across the region late Boxing Day evening and overnight into Sunday.
A severe warning for rain was also issued which covers Mid Wales, but not Shropshire, as well as parts of Scotland and much of north and south west England on Saturday.
#StormBella brings increasingly wet and windy weather across the UK this afternoon. Heavy rain is falling across western Scotland, and the wind will strengthen to gale force in places.— Met Office (@metoffice) December 26, 2020
Latest warning info 👉 https://t.co/QwDLMfRBfs Stay #WeatherAware pic.twitter.com/XobzY6XEqG
Three flood alerts were in place in Shropshire - for the River Severn from Shrewsbury to Bridgnorth, the Severn Vyrnwy confluence from the Welsh border to Shrewsbury and for the River Worfe in the Shifnal and Cosford area.
The River Severn has been dropping since peaking in Shropshire on Christmas Eve but was expected to rise again as a result of the rain brought by Storm Bella.
It peaked at 3.13m at Welsh Bridge in Shrewsbury on Christmas Eve morning, at 4.87m at Buildwas at lunchtime and at 4.15m at Bridgnorth in the evening.
The flood alert service said flooding was likely to affect low lying land and roads the length of the Severn from Shrewsbury to Upper Arley, while Llanymynech, Maesbrook and Melverly could be affected by the Severn/Vyrnwy confluence.
A spokesman said: "We expect river levels to remain high through the weekend. We are closely monitoring the situation. Please avoid using low lying footpaths and roads near local watercourses and avoid contact with flood water."
As of 5am on Boxing Day, England had 78 flood warnings and 99 flood alerts, two flood warnings and five flood alerts were in force in Wales, and seven warnings and 13 alerts had been issued by the Scottish Environment Protection Agency.
Parts of the country were already sodden after recent wet weather and flooding, with residents in more than 1,300 properties along the River Great Ouse in Bedfordshire advised to leave their homes as water levels rose on Christmas Day.
Met Office Deputy Chief Meteorologist Tony Wardle said: “Conditions will turn very unsettled after Christmas day, with a large area of low pressure sweeping across the UK from Boxing Day. Very strong winds will impact much of England and Wales, with particularly strong gusts on south west facing coasts.
“Heavy rain will also move in from the north, with heavy downpours through the afternoon in Scotland and Northern Ireland moving south across England and Wales overnight. This will be a notable change from the calmer conditions over Christmas Eve and Christmas Day so take extra care and stay up to date with the latest forecast.”
Further rain is expected on Sunday and Monday and the area is one of three under a severe flood warning, meaning a danger to life, along with the Cogenhoe Mill caravan site and Billing Aquadrome Holiday Park, both on the River Nene in Northamptonshire.
Bella, which follows relatively calm and cold conditions across the UK on Friday and early morning snowfall recorded in some areas, also led to the Met Office issuing an amber wind warning for parts of south Wales and across southern England on Saturday.
In Ireland, Met Eireann issued a country-wide status yellow wind and rain warning, in force until 4am on Sunday.
Bedfordshire Police on Friday “strongly urged” residents living near the River Great Ouse in north Bedfordshire to seek alternative accommodation due to fears of flooding.
On Christmas Day, Superintendent Steve Ashdown, who is leading the response, said officers had visited just over 1,300 homes in the area the previous evening and officers reiterated the advice on Friday.
“The river is currently at heightened levels and we’re predicting a significant flooding event by 8pm this evening,” he said in a video on Twitter.
“Appreciate the timing of this at Christmas Day is not great, but the risk to you and your family and wellbeing is significant.”
He asked residents able to leave their homes to do so in a “Covid-safe way” if possible, recommending they go to one single location and stay there until it is safe to return in the coming days.