AUTHORITIES across the northern hemisphere issued health warnings and advice on staying hydrated over the weekend as Europe, Asia and America baked in a record-breaking heatwave.

Athenian authorities closed the Acropolis as temperatures in the Greek capital reached 41°C, while heat alerts were issued by 15 Italian cities including Rome, Bologna and Florence. Rome is forecast to hit temperatures of 42°C on Tuesday.

The alerts advise people to avoid direct sunlight between 11am and 6pm. The Italian Red Cross warned that most people are unaware of the health risks posed by such high temperatures.

The thermometer scaled new heights further north too, with the Czech Republic recording a 38.6°C temperature in Plzen-Bolevec on Saturday, the highest ever for a July 15 in the country. In the Polish capital Warsaw, makeshift hose fountains were set up in the streets to help people keep cool.

Ten European countries had their hottest years on record in 2022 — including Britain, France, Italy, Spain and Germany — and EU space observation programme Copernicus said last month that the continent was the fastest warming place on Earth, with temperatures last year being 2.3°C higher than pre-industrial revolution averages. Some meteorologists argue the increasing frequency and severity of heatwaves indicates that a global warming “tipping point” has already been reached.

Wildfires raged in the Canary Island of La Palma and in California,  halfway across the world, where evacuation orders were issued affecting over 1,000 homes. 

The US has issued extreme heat advisories covering more than 100 million people, a third of the population, with temperatures in parts of California, Nevada and Arizona due to hit 48.8°C. Phoenix, Arizona, recorded a 15th consecutive day above 110°F (43.3°C), meaning another three days will beat its all-time record for a prolonged heatwave, set in 1974.

“This heatwave is NOT typical desert heat due to its long duration, extreme daytime temperatures and warm nights,” the National Weather Service warned in Nevada. “Everyone needs to take this heat seriously.”

Sweltering conditions were recorded across Asia from Turkey to Japan. In China and Korea, extreme heat is now combining with heavy rains, and flood warnings were issued in Chongqing and Inner Mongolia.