Warnings of downpours until Thursday night
A Met Office alert covers much of Scotland
Heavy rain could bring flooding and travel disruption across the much of Scotland on Wednesday and Thursday, according to the Met Office.
A yellow warning for rain is in place for the east and south of the country until 6pm tomorrow, with another spanning the north of England, the Midlands and north and mid Wales until 6am.
Another yellow rain warning comes into place at noon on Wednesday for Scotland, covering the south and east of the country, which runs until 6pm on Thursday.
A further yellow warning for thunderstorms has been added for much of the south coast of England from 8am to 7pm on Wednesday.
Met Office meteorologist Alex Burkill said: "Some areas are really going to see a lot of heavy, persistent rain through a big chunk of Wednesday. It is going to be a pretty wet picture as we go through the rest of the week for many places.
"There is some uncertainty as to exactly where we are going to see the heaviest rain and where is most likely to be impacted."
The forecast says heavy and, in places, prolonged rainfall is expected from an area of low pressure which is arriving from the east having brought downpours to parts of central Europe.
Up to 8cm of rain
Many places could see 30-40mm of rain, while a few areas may receive 60-80mm as heavy rain moves northwards throughout Wednesday. The Met Office said there is a small chance a few upland areas could see up to 150mm, most likely across Snowdonia and parts of north Wales.
In addition to the thunderstorm warning, which also includes scattered showers and the threat of spray on the roads and sudden flooding, the south of England could see heavy, thundery showers which could bring 30-40mm within three hours.
A Met Office spokeswoman said: "The precise track of the low pressure which would determine where the rainfall comes is still uncertain and is something we are keeping an eye on.
"We would encourage people to keep an eye on the forecast over the next couple of days to see how that evolves."
Chief meteorologist Andy Page said areas exposed to the strengthening northerly winds are most likely to see the highest rainfall.
Northern areas are expected to remain cloudy and wet on Thursday but drier further south with brighter conditions becoming more widespread by the end of the week.
Bank Holiday Monday is expected to be dry and fine for much of the country, feeling warm in the sunshine, although there remains the threat of showers ahead of more settled conditions.