The Met Office is forecasting heavy rain across Lincolnshire this Thursday and Friday.
The rainfall is likely to be heavy and thundery at times, with the potential for torrential downpours in places.
The chief forecaster said an area of low pressure is expected to develop just to the northwest of Spain in the next 12 to 24 hours.
This system is then expected to push north across Biscay and into the south of the UK early on Thursday.
With very warm air entrained into the system, locally heavy and thundery rain is likely to develop as the system pushes across parts of England and Wales.
Around 15 to 30 mm of rain is possible in 6 to 12 hours, with as much as 50 mm possible very locally by the end of Thursday.
A developing area of rain is expected to reach the south of England early on Thursday morning, before pushing north across much of southern UK during the day.