The Met Office has warned people in the south to stay indoors if at all possible this evening as a “huge cluster” of thunderstorms threatens to batter the region.
Far removed from Friday’s highs of 32C, the forecaster has issued a rare lightning warning as a cold front from the north moves south.
The storms are currently in the south west but could move into the south east as tonight continues.
People are also warned to stay away from power lines or exposed areas which could be danger areas for lightning strikes.
Meteorologist Beck Mitchell: “It felt like it was just getting into summer but it's cooler now.
"Lots of places in the UK have seen a temperature drop of about 10 to 15 degrees in some places, which is massive.
"We've got a huge cluster of thunderstorms in the south west of England, there's potential we could see some in the South East later on tonight."
"If you are doing any outdoor activities move inside if you can - that's the best advice really.
"Stay away from any power lines or anything like that which could potentially be struck by the lightning.
"If you do find yourself in an exposed location, stay close to the ground, away from anything which could conduct lightning."
Lightning warnings have only been issued three times previously, with the last in 2019.
The mercury rose to 33C in parts of the South East on Friday due to the hot air moving north from Iberia and saw hot temperatures across much of the UK.
Sunday’s outlook is set to be bright with spells of sunshine for most places at some point during the day, especially later on.
There is a chance of showers developing - mainly to the south - which could be heavy and thundery on the south coast of England.
It is mostly dry during the evening with fresh, north-westerly winds expected.
The mid 30s temperatures will not be returning for the immediate future, although the mercury could nudge the mid 20s in time for the Glastonbury Festival next week.
Ms Mitchell added: “It looks like the start of Glastonbury, particularly Wednesday or Thursday, is likely to be dry hot and sunny
"For anyone setting up your tent it's likely to be quite good weather.
"Heading into the weekend from Friday onwards it looks like we could see more in the way of showers, probably some sunny spells and showers."
While the top temperature was 32.7C on Friday, the highest on Saturday was 27C in Herstmonceux, East Sussex, and there were showers in many places, with the Met Office issuing a yellow warning for south west England as the lightning and heavy rain approached.
