The hottest day ever in the UK could be recorded in the next day or so as temperatures continue to soar - and the Government is being warned it must do more to protect vulnerable people in extreme heat.
The mercury is set to hit 35C in parts of the UK on Thursday and rise further to 37C on Friday, triggering a thunderstorm warning into the afternoon.
There is a chance the high temperatures could even beat the all-time UK record of 38.5C, the Met Office has said.
Temperatures in the North East are set to reach a more modest - but still sweltering - level of around 28 degrees today and 26 degrees tomorrow - with a muggy feel, and thunderstorms on the cards later in the day on Friday.
Children, the elderly and people with lung or heart problems have been advised to reduce strenuous exercise and physical exertion in the hottest parts of the country.
Meanwhile, Health Secretary Matt Hancock has been urged to set out what measures he is taking to make sure the NHS can cope with the heatwave.
Shadow health secretary Jon Ashworth said hospitals are facing year-round pressures, saying "the traditional lull in NHS activity during the quieter summer months is a thing of the past".
Blood supplies have dropped, health officials have said, saying some people have been too dehydrated to donate while others have chosen to stay in the sun.
MPs have warned heat-related deaths will treble by mid-century unless the Government takes action to tackle the dangers of soaring summer temperatures.
Without the Government developing a strategy to protect vulnerable people, such as the elderly, numbers dying from the heat could rise to 7,000 a year by 2050, a report from the parliamentary Environmental Audit Committee said.
The committee called on the Government to take action to ensure homes, hospitals, care homes, offices, cities, water supplies and transport networks can cope with rising temperatures.
Scientists have warned that climate change is making such heat extremes more likely, and the report comes as northern Europe swelters in a prolonged heatwave.
Wildfires in Greece have claimed the lives of at least 80 people, including Irishman Brian O'Callaghan-Westropp, who was there on honeymoon.
He and his new wife Zoe Holohan, who is in hospital after suffering burns to her head and hands, had flown to Greece on Saturday following their wedding in Co Meath two days earlier.
An amber "heat health watch" warning remains in place for parts of England, with people being warned to try to stay out of the sun between 11am and 3pm.
Following the driest first half of summer on record, farming leaders warned crops are being hit and livestock are having to be fed with feed that should be held for winter as grasslands are parched.
The dry spell has been most prolonged in East Anglia and south-east England where the last day of very widespread rainfall was seen on May 29.
Firefighters have urged the public to avoid "careless and reckless" behaviour during the ongoing heatwave as crews across the country deal with a high number of field fires.
The thunderstorms could lead to flooding of homes and businesses, difficult driving conditions and potential power cuts, the Met Office warned.
Scotland and Northern Ireland have been experiencing recent temperatures nearer normal for the time of year.
Paul Gundersen, chief meteorologist at the Met Office, said: "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."