NEW YORK - Heatwaves intensified across southern and eastern Europe, Asia, and much of the United States on Tuesday as the World Meteorological Organisation warned of an increased risk of deaths due to the extreme weather.

Americans were facing a medley of extreme weather, from blazing heat from Texas to Southern California to smoke-choked air wafting into the Midwest from Canada’s wildfires.

Flood warnings were up for Vermont towns that were inundated just last week, while Tropical Storm Calvin was expected to hit the Pacific island state of Hawaii later on Tuesday.

The southwestern city of Phoenix, Arizona, on Tuesday exceeded 110 deg F (43 deg Celsius) for the 19th day in a row, breaking its all-time record of 18 straight days over 110.

As temperatures in the Arizona capital climbed to 116 deg F (47 deg C), out-of-state visitor Amit Ghagoji, 40, set out for a hike in the trails of Phoenix’s Papago Park.

“It’s like you open an oven door and it’s the heatwave,” Mr Bhagoji said. “If you’re, like, making cookies or something, and you open the oven door, it’s going to hit you right in the face.”

Mr Tom Frieders, a meteorologist at the National Weather Service in Phoenix, said regional high temperatures would range between 115 deg F and 120 deg F for five to seven more days if not longer.

“It’ll take probably some monsoon thunderstorms and cooling rains to come – hopefully, eventually – that will help to cool things down,” Mr Frieders said.

Meanwhile, in the northeastern state of Vermont, thunderstorms were expected to drench areas already saturated from recent torrential rainfall, and potentially cause more floods like the ones that overwhelmed roadways and trapped people in their homes last week.

The Mediterranean island of Sardinia could see highs of more than 47 deg C and forecasters said, temperatures could hit 40 deg C in several Italian cities, including 42-43 deg C in the Lazio region that includes Rome.

With baking temperatures hitting Europe during the peak summer tourist season, the World Meteorological Organisation (WMO) said the heatwave in the northern hemisphere was set to intensify. An estimated 61,000 people may have died in heatwaves last year in Europe alone.

The World Health Organisation’s regional director for Europe, Hans Henri P. Kluge, said the world must look ahead while adapting to the “new reality” of killer heatwaves and other extreme weather.

“There is a desperate and urgent need for regional and global action to effectively tackle the climate crisis, which poses an existential threat to the human race,” he said.

The EU’s emergency response coordination centre issued red alerts for high temperatures for most of Italy, northeastern Spain, Croatia, Serbia, southern Bosnia and Herzegovina, and Montenegro.

Heatwaves this summer, which saw temperatures climb to 53 deg C in California’s Death Valley and over 52 deg C in China’s north-west, have coincided with wildfires from Greece to the Swiss Alps and deadly flooding in India and South Korea.

They have added fresh urgency to talks this week between the United States and China, the world’s top greenhouse gas polluters.

US climate envoy John Kerry met Chinese officials in Beijing and expressed hope that climate cooperation could redefine troubled ties between the two powers.

Chinese President Xi Jinping stressed Beijing’s commitment to carbon neutrality and a carbon peak was certain but that it would not be influenced by others.

“Temperatures in North America, Asia, and across North Africa and the Mediterranean will be above 40 deg C for a prolonged number of days this week as the heatwave intensifies,” the WMO said.

Overnight minimum temperatures were also expected to reach new highs, the WMO said, creating the risk of increased cases of heart attacks and deaths.

“Whilst most of the attention focuses on daytime maximum temperatures, it is the overnight temperatures which have the biggest health risks, especially for vulnerable populations,” it said.

Hottest summers on record

Scientists have long warned that climate change, caused by greenhouse gas emissions mainly from burning fossil fuels, will make heatwaves more frequent, severe and deadly. They say governments need to take drastically reduce emissions to prevent climate catastrophe.

The European Union’s Copernicus Climate Change Service says 2022 and 2021 were the continent’s hottest summers on record. Europe’s highest recorded temperature of 48.8 deg C was registered in Sicily two years ago.

In Italy, tourists have tried to keep cool by splashing in Rome’s fountains and standing under giant fans set up outside the Colosseum. Some were forced to queue for taxis for more than an hour in the heat outside the central railway station in Rome due to the capital’s chronic shortage of cabs.

The health ministry issued red weather alerts for 20 of the country’s 27 main cities on Tuesday, with the number expected to rise to 23 on Wednesday.

“It is not ruled out that we will exceed 47 degrees, and there could be some places in Sulcis and Campidano (in southern Sardinia) that could make us record an even higher value,” said Mr Carlo Spanu, from the Italian air force’s weather service.

The heat has prompted some travellers to go home early. Mrs Anita Elshoy and her husband returned to Norway from their vacation spot of Vasanello, a village north of Rome, a week earlier than planned.

“(I) got a lot of pain in the head, legs and (my) fingers swelled up and I became more and more dizzy,” Mrs Elshoy said, of her heat-related symptoms.

Areas of the northeastern Spanish regions of Catalonia and Aragon, and the Mediterranean island of Mallorca were on alert for temperatures over 40 deg C on Tuesday. The Catalonian Weather Service said the mercury reached 45 deg C at the Boadella reservoir near the village of Darnius, the highest temperature ever recorded in the region.

“I kind of struggled, but I have a ceiling fan and it helped me, I was able to sleep but it was hard,” said Mercedes, a 60-year-old secretary in Madrid.

In Greece, authorities told citizens close to a forest fire in Dervenochoria, north of Athens, to shut doors and windows as smoke approached.

Standing in his burned-out house in Ano Lagonissi that had been his home for 32 years, Giorgos Nikolau, 89, described how he fled the fire with just the swimming trunks and shirt he was wearing.

“I have nothing else, I don’t even have other shoes. Nothing. I am finished,” he said. REUTERS