The danger of frequent lightning from thunderstorms accompanied by sharp downpours of rain are the main hazards we're being warned about, in a series of weather warnings issued today (Friday, 23 July).
A string of notices from the Met Office also carries warnings about high winds expected for a time in Sussex between 3pm today and midnight.
But by far the greater concern from Britain's official forecasters is the effect of powerful thunderstorms, including the potential for flooding.
The thunderstorms are predicted to fall into two groups: one possibly covering Sussex between 8pm tonight and 10pm on Saturday night.
Then there is a further warning of similar weather likely on Sunday between 9am and midnight.
The detail in the Met Office 'yellow' warning, meaning "be prepared", is precise:
"Heavy rain and thunderstorms will move into southern areas during Friday night, reaching south Wales and the Midlands early on Saturday.
"This is likely to bring frequent lightning, possible large hail and gusty winds as well as torrential rainfall for some.
"Where this occurs, perhaps most likely in central parts of southern England, 25 to 35 mm of rain could fall within an hour, with possible flooding.
"Further slow-moving thunderstorms will develop by Saturday afternoon across southern counties of England, easing only slowly through the evening.
"Not all places affected but where they occur, a renewed threat of torrential rainfall and flooding, some locations seeing 30 to 50 mm within an hour or two.
"Lightning, large hail and locally gusty winds could pose additional hazards."
Disruption, forecasters said, could include rapid flooding of homes and businesses, power cuts, and difficult driving conditions.
The winds will mostly be felt before thunderstorms, with some places possibly seeing gusts of 45 to 55 mph, especially along exposed coasts and near and over hills.
As for Sunday's storms, these are mostly expected in Sussex along with the rest of southern and eastern England, and south-east Wales, after early morning rainfall.
Forecasters added that, on the 25th:
"Torrential downpours may develop in some places with hail and gusty winds as additional hazards.
"Rainfall amounts will vary considerably from place to place, but there is the potential for up to 80-100 mm to build up in some locations over the course of the day."
Using data collected by the German weather service Deutsche Wetterdienst, the animated map above shows the potential for thunderstorms to develop, starting on Saturday morning.
The more yellow the colour, the higher the possibility.
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