Greece closed the ancient Acropolis during the hottest part of the day on Friday to protect tourists as southern Europe suffered in a fierce heatwave, while more than 100 million Americans also faced a prolonged spell of sweltering weather.
The European Space Agency (ESA), whose satellites monitor land and sea temperatures, has warned that Italy, Spain, France, Germany and Poland are all facing extreme conditions.
It's almost 50 degrees in some European cities
Temperatures next week could break Europe's current record - 48.8 degrees Celsius recorded in Sicily in August 2021.
Italian meteorologists have dubbed the next phase of the European heatwave "Charon" - a reference to the ferryman of the souls of the dead in Greek mythology. That succeeds this week's "Cerberus" named after the three-headed dog of the underworld.
Parts of Germany will heat up on Saturday. Temperatures will rise to 30 degrees Celsius and 37 degrees Celsius in the eastern and southern regions of the country, according to the German Weather Service (DWD).
Experts point to climate change.
"Extreme weather events, which are occurring with increasing frequency in our warming climate, have significant impacts on human health, ecosystems, economies, agriculture, and energy and water supplies," said the World Meteorological Organization (WMO) Secretary-General Petteri Taalas in Geneva.
"This underscores the increasing urgency to reduce greenhouse gas emissions as quickly and as profoundly as possible."
The world recorded its hottest day ever last week, with scientists blaming the combination of long-term global warming caused by greenhouse gases, with the short-term boost from El Niño, a regular warm-weather pattern originating in the Pacific.
Homeless Americans are being treated for burns
In many places in the southwest of the United States, where hot summers are the norm, extreme temperatures that could break records are forecast in the coming days.
A pregnant visitor shields herself from the sunlight during a tour of the Griffith Observatory in Los Angeles on Friday, 14 July 2023. Source: AAP / Damian Dovarganes/AP
In Mexicali, a city of over a million people on Mexico's northern border across from California, temperatures soared to 50 degrees Celsius this week, forcing many residents to stay inside.
"This weekend there will be some of the most serious and hot conditions we've ever seen," said David Hondula the city's chief heat officer. "I think that it's a time for maximum community vigilance."
The heat was expected to continue well into next week as a high-pressure dome moves west from Texas.
People were wheeled on golf carts in Athens
In Athens, with temperatures peaking above 40 degrees Celsius, authorities closed the Acropolis Hill, home to the Parthenon temple that is visited by millions of tourists every year, from noon to 5pm.
Greek authorities were forced to shut the Acropolis in Athens because of extreme heat on Friday. Source: AAP / Petros Giannakouris/AP
One woman seated on the ground was attended to by paramedics after feeling faint. Others were brought down from the Acropolis Hill in golf carts and transferred to wheelchairs.
Greece's civil protection ministry warned of the risk of forest fires in five areas and told people to avoid tasks such as burning weeds for fear of setting off blazes. Wildfires also hit parts of Croatia close to the Adriatic coast.
Last month was the hottest June on record, according to the EU's climate monitoring service Copernicus.
