Almost a month’s worth of rain is expected to lash parts of the UK on Friday.
Forecasters have issued a yellow warning for between 8am and 10pm, with transport likely to be affected and flooding possible.
The warning covers Wales, north west England and south west England, with high ground expected to see the worst weather.
Met Office forecaster Marco Petagna said up to 80mm of rain is possible in some areas.
The average August rainfall in Wales is 107mm and the average for August in the south west is 90mm - meaning almost a month’s worth of rain could fall on Friday alone.
"August actually can be a fairly wet month," he said.
Strong winds are also expected, with 30mph-40mph gusts likely around exposed coasts and hills.
Heavy rain may coincide with peak travel times during the afternoon and early evening, leading to difficult driving conditions on major routes, the warning says.
Mr Petagna said places outside the warning area will not escape the rain on Friday.
"Much of England and Wales will see a fairly wet day," he said, adding that the whole of the UK will get rain at some point.
The forecaster said the weekend will bring sunshine and blustery showers, adding that things are looking more positive next week.
"Especially come mid-week, pressure’s building a bit," he said.