A yellow weather warning issued by the Met Office remains in place for a stretch of eastern England until 07:00 BST on Friday.
People in this area could see frequent lightning, hail and strong, gusty winds in addition to heavy rain.
For the rest of the day expect showers and longer spells of rain, with heavy downpours and thunderstorms possible, especially across western Scotland, Wales and north-west England.
Some of this wet weather could spread east later, with thunderstorms possible across north-east England and eastern Scotland.
After the recent warm and humid conditions, temperatures by Friday will feel fresher.
Expect around 20–23C (68 -73F) in England and Wales, and 16–20C (61-68F) in Scotland and Northern Ireland.
These temperatures are around average for late August.
