Temperatures will soar again on Sunday as the second amber heat health alert in two weeks remains in force.
The mercury could hit 30C in London, 28C in the east of England, and 28C in the Midlands, the Met Office said.
But temperatures will remain relatively low in other areas, with 21C the highest likely to be reached in Scotland, and 23C in the south-west of England.
Sunday will see a band of cloud and rain across central parts of the UK, gradually edging northwards.
This rain may ease for a time before turning heavier in the far northwest later in the day.
Southern areas will start cloudy with some patchy drizzle on western hills, but there will be plenty of dry weather too, with sunny spells developing.
It comes as a second amber heat health alert in two weeks came into force on Friday.
The alert, which covers London, the East Midlands, South East, South West and East of England, will last until 6pm on Tuesday.
The UK Health Security Agency (UKHSA) also issued a yellow alert for Yorkshire and Humber and the West Midlands for the same time period, with the agency warning of significant impacts across health and social care services.
Temperatures could reach 34C on Monday, which if it did, would only be the fourth time in June since the 1930s.
The June record, which could be surpassed, stands at 35.6C, recorded at Southampton Mayflower Park on June 28 1976 and again at Camden Square, north London, on June 29 1957.
An amber alert was previously issued for all regions in England on June 19, the first time it had been used since September 2023.
On the same day, temperatures reached 32.2C in Kew, west London, before heatwaves were declared across England and Wales.
An official heatwave is recorded when areas reach a certain temperature for three consecutive days, with thresholds varying from 25C to 28C in different parts of the UK.
