The Met Office is warning that after a scorching day on Friday, heavy thundery showers will develop on Saturday, with the threat of localised flooding in Nottinghamshire.
Forecasters say that areas of heavy, thundery showers may develop over England and Wales from early on Saturday before moving northwards during the day.
The development of these is uncertain but where they do form some torrential downpours are possible with frequent lightning, hail and locally strong gusts.
Significant flooding is possible where these do occur from surface water as well as small, fast responding watercourses. The frequent lightning, hail and strong gusts could also be an additional hazard.
The Met Office add that the public should be aware of the risk of disruption from any of these elements.
Forecasters say they may update their severe weather alert in the coming days.