Storm Francis is sweeping across the UK bringing “unseasonably” strong winds, heavy rain and flooding.
Weather warnings are in place for rain and wind, with the heaviest downpours expected across Northern Ireland and south-west Scotland.
Forecasters believe up to 90mm of rain could fall, while gusts of up to 70mph are predicted in England and Wales.
Homes have already flooded in south Wales, and people have been warned of travel disruption.
As of 08:00 BST, gusts of 55mph had been recorded at Mumbles, on the Gower Peninsula, according to BBC Weather.
Plymouth, on the south Devon coast, also recorded gusts of 53mph on Tuesday morning.
The Met Office said there were “large” rainfall totals overnight, resulting in a lot of surface water.
Some 46.9mm of rain fell in White Barrow, in Devon, and a total of 46.4mm was recorded in Glamorganshire, it said.
Met Office forecaster Alex Deakin said it would be “wet and windy for large chunks of the UK”.
“The bands of rain [will] move into Northern Ireland and stick around, move into Scotland and hang around for most of the day,” he added.
Further south, rain is expected to clear to blustery showers during the day, with the chance of a few brighter spells emerging later in the day in the south and southeast of the UK.
But “unseasonably” strong winds are also expected, with England and Wales likely to see the highest gusts, according to the Met Office.
Storm Francis comes on the back of Ellen which struck last week and caused power outages. It marks the first time the Met Office has had two named storms in August since it started the process in 2015.
Forecasters said the winds were “unusual” for August, but would have to go some way to beat the current record wind gust speed of 87mph recorded at The Needles on the Isle of Wight in August 1996.
Likewise, the wettest August on record in the UK was in 1912 when 167.3mm was recorded across the country as a whole.
Between 1 and 22 August, the UK as a whole had seen some 72.7mm of rainfall – around four-fifths of the average rainfall for the month.
No new storm is currently forecast this month, meaning the next storm will begin with A rather than G, as the storm-naming calendar resets on 1 September.