Thunderstorms moved into southern and western areas late on Tuesday evening, with the Met Office issuing a yellow severe weather warning for most of England, Wales and Scotland until 9am on Wednesday.
Surrey Police posted a video of what it called "a great lightning show" and some Twitter users posted to say they had been woken up by the thunderstorms.
Read more from Yahoo News UK:
North Wales was the wettest area overnight, getting 15mm of rain in one hour.
But by Wednesday morning, much of the country was already experiencing temperatures far above normal for this time of year.
The lightning storm came as Met Office forecasters predictors temperatures of 39C on Thursday.