GEOFF BENNETT: A major heat wave is shattering records across Europe, leaving tens of millions of people under sweltering conditions.

France topped a record for the country's hottest day ever for the second consecutive day, and the U.K.

and Spain both hit record highs for the month of June.

Stephanie Sy has our report.

STEPHANIE SY: In London today, the temperature hit 96 degrees, and outdoor workers felt it.

JOHNNY O'CONNOR, Construction Worker: Awful, to be honest.

It's horrible, this heat.

STEPHANIE SY: These kids didn't seem to mind the heat much.

A spray-down was also in order for this crowd waiting in line to attend a concert in Milan, Italy.

At the Vatican, the faithful fluttered their fans while Pope Leo held his weekly audience.

And while the beer may still be cold in Munich, in the kitchens, the chickens weren't the only ones roasting.

SASCHA MEYER, Beer Garden Manager (through translator): Just run quickly to the sink and splash your face with cold water.

Then drink loads of water.

That's our little secret.

STEPHANIE SY: Today, more than a dozen countries in Europe were under high heat alerts in the second major heat wave for the continent in two months.

A heat dome, a high pressure system trapping hot air, is covering the region, says Clair Barnes, an extreme weather and climate researcher at Imperial College in London.

CLAIR BARNES, Research Associate, Imperial College: It means that it's drawing warm air up from North Africa, from the Sahara, and that's why we have this really intense heat, and it's very slow moving, and it means there's kind of no winds, no breeze for respite.

STEPHANIE SY: With temperatures reaching more than 110 degrees, France has been on the front line.

Heat-related deaths are climbing, including 40 drownings in recent days that authorities attribute to people seeking relief in rivers and lakes.

ZOUZOU HOBBS, Tourist in Paris: My friend who lives here says she's -- there's no way she's going to be swimming in hooks, because it's so dirty, but it's hot.

I'm going to risk it.

STEPHANIE SY: Earlier this week, police in Paris tried to stop young people from turning a footbridge into a diving board.

The Eiffel Tower and the Louvre were shut down early, and the classic gray zinc roofs that cover much of the skyline are making things unbearable for those living in attic units.

AMELIE KENNY, Parisian Student: It's been the worst week that we have had in this apartment.

STEPHANIE SY: Air conditioning is a rarity across Europe, making fans a hot commodity.

VICTORIA YAKUBOV, Filmmaker (through translator): It's pure coincidence that I have this electric fan because someone left it aside.

Everything was gone in less than 30 minutes.

STEPHANIE SY: For decades, many European countries didn't need air conditioning since extreme heat was relatively rare.

But, more recently, environmental concerns, energy costs, and health worries have all been part of the resistance to A.C.

Oscar Brousse works on urban climate and health at the University College London.

OSCAR BROUSSE, University College London: Adding air conditioning on the energy grid would require basically more energy to be produced when -- during cooling hours, which is something that the E.U.

has been trying to prevent to not have to rely, for example, on fossil fuels to cope with this energy demand.

STEPHANIE SY: Europe is the world's fastest warming continent.

Temperatures have been increasing at twice the speed of the global average since the 1980s.

OSCAR BROUSSE: There has been heat waves, of course, in the past already, but their intensity and their frequency has become really problematic due to global climate change, and especially supraregional or would I say continental climate change that we experienced in Europe.

STEPHANIE SY: More than 200,000 people have died from heat-related causes in the past four years across Europe.

Many countries are taking care to engage elderly populations, who are more vulnerable to heat-related illnesses.

These Italian seniors had their morning workout moved to an air-conditioned space.

And movie theaters in Geneva are offering free daytime screenings for the elderly.

LAURENT DUTOIT, Cinemas Manager (through translator): The hotter it gets, the more the cinema becomes a place of refuge.

So we will also have a few more people, I imagine, in the coming days.

STEPHANIE SY: In Madrid, the city reopened its climate shelter in city hall for the third year in a row, offering cool air, food, water, and a place to shower for the homeless.

JUAN CARLOS ARELLANO, Samur Social, Madrid (through translator): On Saturday, one person came.

Yesterday, three came.

Our experience from previous years is that, as the days go by, many more people start coming.

I seem to recall that, last year, we had around 170 people.

STEPHANIE SY: Experts say this is likely just the start of this summer's heat across Europe and the globe.

OSCAR BROUSSE: In the U.K., we have broken records nearly every year now.

These are things that we don't see usually and that we know are related to global climate changes.

So we could expect future summers to become warmer, and more regularly so.

STEPHANIE SY: For the "PBS News Hour," I'm Stephanie Sy.