A heat alert warning has been issued by the Met Office and UK Health Security Agency (UKSA) as temperatures are set to soar to 34C later this week.
The forecaster said a level 2 alert has been issued for southern and central England from midnight on Friday until midnight on Sunday, with a lower level 1 alert in place for northern England.
The alert system is designed to help healthcare workers manage through extreme temperatures.
The Met Office warned earlier this week that Britons should brace themselves for heatwaves over the coming months, amid previous research by the forecaster indicating that they were becoming more likely due to climate change.
Forecasters said southern parts of the UK could hit 30C (86F) and even top 34C (93F) in the south-east, while in the north-east and north-west temperatures are predicted to jump to 28C (82F).
The highest temperature reached in the UK so far this year was 27.5C (81.5F) at Heathrow on 17 May.
Met Office deputy chief meteorologist Dan Rudman said the temperature predictions are unusual for this time of year.
“Many areas will also see some warm nights with minimum temperatures expected to be in the high teens or even low 20Cs for some overnight,” he said.
“The heat is a result of a mix of home-grown warming in the day due to high pressure, as well as a southerly airflow introducing some of the warm air from the continent to UK shores.”
A heatwave is defined as three consecutive days of daily maximum temperatures meeting or exceeding the heatwave temperature threshold. The threshold varies in each county.
In March the heatwave thresholds were increased in eight counties by the Met Office in response to the warming climate that made the original thresholds obsolete.
Agostinho Sousa, head of extreme events and health protection at the UKHSA, said: “Temperatures are forecast to reach 30C in some parts of the south on Friday and we want everyone to enjoy the hot weather safely when it arrives and be aware of good health advice for coping with warmer conditions.
“During periods of hot weather it is especially important to keep checking on those who are most vulnerable, such as older people and those with heart or lung conditions.”
An Environment Agency spokesperson said there is a low-risk of drought but warned further hot, dry weather could put pressure on some areas.
NHS hot weather advice suggests that people stay out of the sun between 11am and 3pm, keep hydrated, use sunscreen and wear loose-fitting clothes.
