Nottinghamshire has been issued with a yellow warning for thunderstorms expected to start at midnight, lasting until 6pm.
It adds: "Some places could see 15-20 mm in an hour, and perhaps up to 50 mm before storms fade, and hail may affect a few spots. These thunderstorms will slowly spread into southern parts of northern England on Sunday morning before easing.
"Further south, drier conditions briefly develop on Sunday morning before further showers and thunderstorms develop over some parts of southern England, Wales, the Midlands and East Anglia later.
"These may give some heavy downpours with a further 10-20 mm possible in some places."