Temperatures could hit 20C in parts of the UK on Wednesday, while flooding is possible as a yellow weather warning for heavy rain continues, the Met Office said.

Mild weather is forecast for Wednesday, with highs of 20C or 21C in the south – about 5C warmer than the average for this time of year – while 13-18C is forecast for most, the forecaster added.

And a yellow weather warning for rain is in place until midday on Wednesday, stretching from Plymouth and reaching as far north as Manchester, covering parts of north-west and south-west England, Wales and the West Midlands.

Over the last 12 hours, about an inch of rainfall has been seen widely across the warning area, with 10-20mm forecast to continue for many areas and 50mm could be seen locally, Met Office meteorologist Greg Dewhurst said.

The forecaster warned spells of heavy rain could lead to travel disruption and flooding in places.

Mr Dewhurst said: “Outbreaks of rain have been pushing north across the night, the weather warning is in place until midday.

“The rain is quite extensive across parts of Scotland, Northern Ireland, Wales and the west of England, and when it’s not raining it’s cloudy, misty and murky.

“It will stay pretty similar in terms of the areas that will see the outbreaks of rain, it could be heavy at times.

“The driest will likely be across the east and south-east of England.

“It will start to become drier across the south-western parts overnight; by the end of the night it will be more restricted to parts of Scotland and north-east England.

“Tomorrow there will be rain first thing across Scotland and north-east England. It will quickly clear and be a much brighter day for everyone. There will be a few showers but lots of places will stay dry and temperatures will be between 16-19C.”

The forecaster added that on Friday there will be a west and east split developing with cloud and rain in western parts of the UK while central and eastern areas will be dry with sunny spells. Temperatures will be between 13-16C.

The warning comes after heavy rainfall caused widespread flooding across the UK in September and early October.

Some counties of England saw their wettest September on record, receiving three times the normal rainfall, and Oxfordshire and Bedfordshire had their wettest months ever – although the rain came after a drier than normal summer for much of the UK.