Some public health experts have predicted that hundreds if not thousands of people could die in the UK before temperatures plummeted into the high 70s on Wednesday. During a heat wave in 2003, some 2,000 people died from the heat in the UK and 15,000 in France.

“I’m afraid the additional deaths are to be expected on Monday and Tuesday” in the string of “thousands of deaths,” Sir David King, the former British government chief scientist, told LBC radio. He said this could be “up to 10,000” dead.

“Even as a climate scientist studying this sort of thing, this is scary,” said Professor Hannah Cloke, a natural hazard researcher at the University of Reading, told NBC News’ UK partner Sky News on Monday. “This feels real. At the beginning of the week I was afraid that my goldfish would get too hot. Now I worry about the survival of my family and my neighbors.”

The government-funded National Health Service, already under pressure from Covid-19 and long-term capacity issues, is reporting that some operating rooms have suspended operation until temperatures are under control, Miriam Deakin, deputy director of the membership organization NHS Providers, told Sky News.

The extreme heat meant that “the NHS is planning for, and seeing, increased demand for emergency and emergency care to accommodate that,” Deakin said.

In an effort to avoid mass casualties, the government has advised people to stay indoors, close windows and curtains and watch out for elderly or vulnerable neighbors. Newspapers published “heat wave hacks,” telling people to cover their windows with aluminum foil and place ice near their cooling fans.

Rising temperatures are already impacting travel, with London’s Luton Airport saying on Monday it has suspended flights after brutal conditions affected the runway.

“After today’s high temperatures, a surface defect was identified on the runway,” the airport said in a statement. “Engineers were immediately called to the scene and repair work is currently underway to resume operations as soon as possible.”

The Royal Air Force was also forced to suspend flights at Brize Norton base due to the heat wave, saying in a statement Monday that planes are using alternative airfields and that “there will be no impact on RAF operations.”

And authorities are urging drivers to stay off the roads in the middle of the day, while some local authorities are deploying salt trucks to spray sand onto the asphalt to try to stop the melting.

Network Rail, which manages the country’s train infrastructure, asked people not to travel, warned that the heat could buckle the tracks and announced that there were speed limits.

Elsewhere, utilities said they were monitoring potential blackouts and water shortages.

Some schools close earlier and kids get a day off from their starchy, buttoned-up uniforms that are common here.

Meanwhile, France’s southwestern region of Gironde is one of the litany of European regions currently on fire. The wildfires there have spread to 27,000 acres — more than half the size of Washington, DC — and 14,000 people have fled their homes.

“This is not ‘just summer’,” French senator Mélanie Vogel tweeted. It’s “just hell” and will become “just the end of human life” pretty soon if we continue our climate inactivity.”

In Portugal, another place where wildfires rage, more than 650 people died at temperatures above 116 degrees.

Fire officials in Greece said on Saturday that 71 fires had broken out in the past 24 hours.

A study published in June in the journal “Environmental Research: Climate” concluded that climate change was highly likely to exacerbate heatwaves, according to Reuters.

Reuters contributed.