The Met Office has issued a yellow warning for thunderstorms for the East of England.
The warning covers Bedfordshire, Buckinghamshire, Cambridgeshire, Essex, Hertfordshire, Norfolk, Northamptonshire and Suffolk and is in place from 11:00 BST until 20:00.
The Met Office said poor driving conditions and train delays were possible.
A spokesperson said: “Scattered heavy showers, some with thunder, are expected to develop later this morning and into the afternoon, before easing this evening.”