Very hot conditions will continue across central, eastern and south-eastern parts of the England until the end of the week, but the heat will trigger intense thunderstorms in some areas.
The Met Office says that the heatwave of 2018 will reach a peak for the time being on Thursday and Friday with temperatures likely to break the UK July record, and possibly the all-time UK record somewhere in south-east England.
Highs of 35degC are expected on Thursday and 37degC on Friday.
Paul Gundersen, Chief Meteorologist at the Met Office, said: “The heatwave conditions will continue across much of England, with temperatures into the mid to high 30s Celsius in many places from the Midlands eastwards on Thursday and Friday and it’s possible that we could break the all-time UK record of 38.5C if conditions all come together.
“If you’re looking for somewhere to escape the heat, western and northern areas will have pleasantly warm mid 20s Celsius, although across Northern Ireland and western Scotland this may be accompanied by occasionally cloudy skies.”
The highest temperature recorded so far this year is 33.3degC at Santon Downham on July 23.
The highest temperature recorded in 2017 was 34.5degC at Heathrow on June 21.
Prior to this, the most recent heatwave prior to this was in July 2015 when temperatures peaked at 36.7degC at Heathrow on July 1, a temperature that is currently the July all-time maximum record.
The all-time record in the UK is 38.5degC at Faversham on August 10 2003.
The dry spell has been most prolonged in East Anglia and South-east England.
The Met Office says that hot weather often brings the risk of showers and thunderstorms and there is a chance of a few of these breaking out over East Anglia, south-east and perhaps central England on Thursday evening.
“It is Friday when we expect the highest chance of intense thunderstorms across eastern parts of England on Friday before the fresher, conditions finally make their way east across the UK for the weekend.”
Gundersen added: “There is the chance of thunderstorms breaking out over some eastern parts of England on Thursday, but it is Friday when we see intense thunderstorms affecting many central and eastern areas.
“Whilst many places will remain dry and hot, the thunderstorms on Friday could lead to torrential downpours in places with a much as 30mm of rainfall in an hour and 60mm in three hours.
“Large hail and strong, gusty winds are also likely and combined could lead to difficult driving conditions as a result of spray and sudden flooding. We have issued a Met Office weather warning highlighting the areas most at risk.”
A Level 3 heat-health watch warning has been issued for a large part of England, in association with Public Health England. The Heat Health Watch Service is designed to help healthcare professionals manage through periods of extreme temperature.
Hot weather, especially when prolonged, with warm nights, can have effects on people’s health and on certain infrastructure.
Dr Thomas Waite, Consultant in Health Protection at Public Health England, said: “Temperatures are likely be high in parts of England this week, which may leave older people, young children and those with long-term conditions, including heart and lung diseases, struggling to adapt to the heat. So keep an eye on friends and family who may be at risk.
“To beat the heat, try to keep out the sun from 11am to 3pm, walk in the shade if you can, apply sunscreen and wear a hat if you have to go out in the heat. Also try to carry water with you when travelling.”