The head of the health service warned that high temperatures could lead to the death of people during the work of the deputy prime minister Dominic Raab said that people should be stable enough to “enjoy the sunshine”.
Tracy Nicholls, chief executive of the College of Paramedics, said the “severe heat” expected to hit the UK over the next few days could have a devastating effect on Britons.
Scorching temperatures are forecast for Monday, with temperatures expected to reach 37C in Peterborough Milton KeynesNorwich and Lincoln the temperature can reach 36C and the temperature can reach 40C London on Tuesday.
Climate attribution scientist MetaburoDr Nikos Christidis said the 40C forecast was a result of climate change.
The forecaster issued an amber warning for most of England on Sunday, which then extends to southern Scotland and Wales from Monday to Tuesday.
The UK’s first red extreme heat warning was also issued by forecasters for much of England from London to Manchester and York on Monday and Tuesday.
The UK’s health agency has also issued a level four heat warning, described as a “national emergency”.
Ms Nicholls told Sophy Ridge On Sky News on Sunday: “It’s not like a lovely hot day when we can put on some sun cream and go out and enjoy swimming and eating outside.
“It’s a serious heat that can ultimately kill people because it’s so fierce. We’re just not set up for that kind of heat in this country.”
Her comments came after Mr Raab said people should take precautions in the face of record temperatures, but added they should be able to enjoy themselves.
“Obviously there’s practical, common sense advice that we’re talking about – stay hydrated, stay out of the sun at the hottest time, wear sunscreen – things like that,” he told Sophy Ridge On Sunday.
“We have to enjoy the sunshine and actually we have to be quite resilient to some of the pressures it’s going to put on.”
Ministers held a virtual emergency Cobra meeting on Saturday after forecasters warned that record high temperatures could put lives at risk.
On Monday and Tuesday, extra emergency support was arranged for emergency services, such as more call handlers and extra hours.
Transport services are expected to be disrupted on both days, with Cabinet Minister Keith Malthouse urging people not to travel.
Avanti West Coast and Transport for London are also urging passengers not to travel unless absolutely necessary.
The chairman of the NHS Confederation, meanwhile, said hospitals would be “really, really pushed” in the next few days.
Lord Victor Adebowale said the NHS would “cope” but added that “coping is not enough”.
He told Times Radio: “My members are quite stressed at the moment. Ambulances are at their peak, waiting times for ambulances are now increasing.
“The NHS will cope, but cope is not good enough. We must actually work in such a way that people can get the treatment they need in a timely manner, wherever they need it. And this is a struggle.”