The UK Met Office has warned that more than half a month's rainfall could hit some parts of the UK in just a 24-hour period this week.
A yellow weather warning for rain comes into effect from 6pm on Monday, and will be in place for 24 hours, covering parts of southwest England and Wales, and stretching to parts of Herefordshire and Hampshire, Sky News reported.
Up to 40mm of rain could fall in some areas and 60-80mm of rain over Dartmoor and high ground in South Wales, which would amount to more than half the average monthly rainfall in December.
The predicted rainfall across southwest England and South Wales is expected to hit already saturated ground and could lead to difficult travel conditions.
More than a dozen flood warnings are in place for England, with two in Scotland and one in Wales.
Meanwhile, a separate yellow weather warning for rain is in place for Northern Ireland on Sunday between 8am and 3pm.
The Met Office's deputy chief meteorologist, Steven Keates, said, "A deepening area of low pressure will approach the UK from the southwest later on Monday, bringing with it heavy rain and strong winds, which are likely to affect the UK between late Monday and early Wednesday.”
"The exact track, depth, and timings of this low are uncertain, which makes it harder to determine where will be most impacted by strong winds and/or heavy rain,” it added.
The Met Office said the rest of the month remained unsettled, with further periods of low pressure predicted.
