Scorching weather gripped three continents on Sunday, whipping up wildfires and threatening to topple temperature records.

In the Vatican, 15,000 people braved sweltering temperatures to hear Pope Francis lead prayer, using parasols and fans to keep cool.

In Japan, authorities issued heatstroke alerts to tens of millions of people in 20 of its 47 prefectures as near-record high temperatures scorched large areas and torrential rain pummelled other regions.

National broadcaster NHK warned the heat was life-threatening, with the capital and other places recording nearly 40 degrees Celsius (104 degrees Fahrenheit).

Japan’s highest temperature ever – 41.1C (106F) first recorded in Kumagaya city in 2018 – could be beaten, according to the meteorological agency.

Some places experienced their highest temperatures in more than four decades on Sunday, including Hirono town in Fukushima prefecture with 37.3C (99.1F).

Meanwhile, the US National Weather Service warned a “widespread and oppressive” heatwave in southern and western states was expected to peak, with more than 80 million people affected by excessive heat warnings or heat advisories on Sunday.

Southern California is fighting numerous wildfires, including one in Riverside County that has burned more than 7,500 acres (3,000 hectares) and prompted evacuation orders.

In Europe, Italians were warned to prepare for “the most intense heatwave of the summer and also one of the most intense of all time”.

Predictions of historic highs in the coming days led the health ministry to sound a red alert for 16 cities, including Rome, Bologna and Florence.

Temperatures are likely to hit 40C (104F) in Rome by Monday and rise on Tuesday, smashing the record of 40.5C (104.9F) set in August 2007.

Meanwhile, at least 4,000 people have been evacuated due to a forest fire on the island of La Palma in Spain.

The ongoing blaze, which started on July 14, has so far devastated more than 5,000 hectares (12,355 acres) of woodland.