The small market town of Gravesend, Kent, basked in temperatures reaching 33.9C (93F) on Wednesday (24 August), as Met Office issued health warnings in south-east and east England.
The south-eastern county also held the previous highest-ever recorded temperatures in the UK, a scorching 38.5C (101F), in Faversham, during the summer of 2003. However, the current heatwave is not set to last.
The Met Office said temperatures on Wednesday 24 August could be followed by thundery showersovernight. Rain showers could fall over much of England and Wales on Thursday, although there will be fine weather in many parts of Scotland and Northern Ireland.
Gravesend often tops the temperature table, mainly due to the sandy soil at Broadness where the MET weather station is sited, and heats up in direct sunshine. In the heatwave of 2003, it briefly recorded the hottest ever temperature in the UK at 38.1 °C (100.6 °F), according to Kent Online.
Met Office forecaster Emma Sharples explained the reason for the hot spell: "It is a combination of strong sunshine and extra warmth being pushed northwards from the continent."
"There will be some thunder storms developing on Wednesday evening into Thursday and we could see some heavy rain. Towards the weekend, there could be an influx of of warm air from the south to send temperatures soaring up."
Dr Thomas Waite, of Public Health England, told the BBC: "Older people, those with underlying health conditions and young children may all feel the ill effects of heat over the coming days," he said.
"We're urging everyone to keep an eye on those you know who may be at risk this summer. If you're able, ask if your friends, family or neighbours need any help."
Meanwhile, five people have died at Camber Sands, East Sussex, after experiencing difficulties while swimming. The fatalities bring the number of deaths around the UK coastline in the past five days to 10.