Heavy rain is expected across the south of England on Thursday morning before pushing north during the day and into Lancashire on Friday.
The warning is active from 6am on Thursday, 13 August, and the rain is likely to be accompanied by thunder and lightning, with potential torrential downpours.
The Met Office are warning the public to be aware of a significant risk of very localised disruption to travel due to surface water flooding.
An area of low pressure is expected to develop just to the northwest of Spain on by Wednesday, heading north across Biscay towards the UK.
15 to 30 mm of rain is possible in in 6 to 12 hours, with as much as 50 mm possible very locally by the end of Thursday.