The UK has had its seventh day of consecutive 30C heat in September, according to Met Office readings.
It comes after Saturday was provisionally the hottest day of the year so far - with highs of 33.2C (92F) recorded at London's Kew Bridge.
Various areas in the East and South East of England such as Cambridge, Rochester and Canterbury reached 31C at around 3pm on Sunday afternoon, according to the Met Office, while the area near London's Heathrow Airport hit 30C around 1pm.
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Beaches along the Kent coast, such as Margate, Broadstairs and Deal, were also extremely busy with sunbathers keen to soak up what might be the last of this year's warmer weather.
The heatwave has already broken the record for the most consecutive days with 30C-plus temperature weather in September, with Saharan dust generating vivid sunsets and sunrises in the clear conditions.
The conditions were called "unprecedented" by Tom Morgan, a meteorologist at the Met Office.
"We have never seen anything as long-lived in terms of a heatwave in September before," he said.
Further north, the Met Office is warning that thunderstorms could bring disruption and a risk of sudden flooding in some areas.
Yellow thunderstorm warnings are in force from 2pm until 11.59pm today - covering much of northern England and Northern Ireland, alongside parts of Scotland and Wales.
The Met Office said a line of "severe thunderstorms" will push northeast across the East Midlands and northern East Anglia, with a small chance that homes and businesses could be damaged by lightning strikes, hail or strong winds.
A similar warning will continue to cover southern Scotland from midnight until the early hours of Monday morning.
Sunday seemingly marks the last day of the heatwave for England, as showers and longer spells of rain will begin to sweep in on Monday - and it's shaping up to be rather unsettled in the South on Tuesday.
Sky's weather producer Chris England said: "It will be cooler and fresher for many, still quite muggy in the South East, although not as hot as recently."