The heatwave will reach a dramatic climax on Sunday – with a yellow warning for thunderstorms in place across large parts of the UK.
Temperatures are set to head above 30C (86F) once again in parts of southern England – with much cooler conditions expected as a new week begins.
But further north, the Met Office is warning that thunderstorms could bring disruption, and a risk of sudden flooding in some areas.
A yellow warning is in force from 2pm to 11.59pm – covering much of northern England and Northern Ireland, alongside parts of Scotland and Wales.
“Unlucky locations” could see up to 70mm of intense rainfall in the space of a few hours – with “additional hazards” of frequent lightning and large hail.
Saturday was provisionally the hottest day of the year so far – with highs of 33.2C (92F) recorded at London’s Kew Bridge.
And Sunday is set to prolong the record for the longest consecutive stretch of September days above 30C, with temperatures above this threshold for the seventh day in a row.
Britons are being urged to make the most of the warmer weather, as conditions are set to become more typical for this time of year.