A yellow warning is in place between 1pm and 10 pm tonight (May 16).
A spokesperson for the Met Office said: "During Monday afternoon thunderstorms are likely to develop over parts of Wales and the Midlands before moving northwards into northern England and develop over Northern Ireland.
"These are likely to bring some heavy rain to places with 20 mm of rain possible in 1-2 hours but also the risk of hail and thunder. The thunderstorms will clear from the south during the afternoon then die out altogether into the evening."
What to expect according to the Met Office
There is a good chance driving conditions will be affected by spray, standing water and/or hail, leading to longer journey times by car and bus
Delays to train services are possible
Some short term loss of power and other services is likely
A chance of some flooding of homes and businesses or some damage to a few buildings or structures from lightning strikes.