Forecasters have warned of thunderstorms and heavy rain for Sunday across much of England and parts of eastern Wales.
As a result, the Met Office reports that there is a "small chance of flooding and disruption" in certain locations.
A yellow warning telling people to "be aware" went into effect for wide parts of southern England, the Midlands, and the north at 04:00 BST. The deadline is 21:00.
Forecasters warn that on Sunday morning, thunderstorms and a lot of rain are expected to start in the south of England and move northward over the day.
The warning covers a region in central England that stretches from the Isle of Wight to Newcastle upon Tyne.
The eastern counties of Wales—Monmouthshire, Newport, Torfaen, and Wrexham—are under alert.
The Met Office said there is a chance of flooding, adding that "frequent lightning strikes and hail will be additional hazards" in southern and central England.
Into Sunday, BBC Weather forecasts that the UK will see some very warm and humid air move in from the south east.
This will also bring some thundery downpours, that will move northward across the central spine of England and east Wales.
These thunderstorms are likely to be quite hit and miss, but where they do occur there could be some torrential rain, as well as strong, gusty winds and lightning.
Although it can be difficult to pinpoint the precise areas of these showers, the BBC weather reports that it is good keeping up with the most recent forecast as it is subject to change.
Many places will have temperatures in the low to mid-20s Celsius due to the warmer and more humid air, with some regions of south east England perhaps seeing temperatures as high as 27C.