Thunderstorms breaking out over parts of Northern Ireland later on Tuesday are expected to extend northeast to affect parts of Scotland overnight and into Wednesday morning.
There is also potential for some severe thunderstorms to develop across Wales, northern England and the Midlands. Here, the risk is greatest during Wednesday, by which time the risk of storms will be reducing across the west of the yellow area - and then finally also reducing across the east of the area by Wednesday evening.
Whilst most places will miss the worst, please be aware of the risk of flash flooding. Frequent lightning, large hail and strong winds could be additional hazards. All of this could lead to some flooding of homes, businesses and transport networks. Disruption to power is also possible.
Chief Forecaster's assessment
Very warm, moist air spreading north and northeast across the western side of the UK is expected to produce thunderstorms later on Tuesday, then transfer eastwards during Wednesday. Rainfall will be very variable, and the extent of thunderstorms is uncertain, but some places could see around 30 mm in an hour and more than 50 mm in a few hours.
Issued at: 1028 on Mon 18 Jul 2016
Valid from: 1700 on Tue 19 Jul 2016
Valid to: 1800 on Wed 20 Jul 2016