Greece was Saturday facing its hottest July weekend in 50 years, with temperatures forecast to soar above 40 Celsius (104 Fahrenheit), while a record-breaking heat wave stretching across the southern United States was expected to expand in the coming days.

According to the Times of Israel, Tens of millions of people in the northern hemisphere have been suffering through intense heat this summer as the world appears headed for its hottest July on record.

As temperature records tumble, experts have pointed the finger at climate change driven by the burning of fossil fuels, saying global warming is playing a key role in destructive weather.

Across the southern United States, about 80 million Americans will swelter in temperatures of 41°C and above this weekend, the National Weather Service (NWS) said.

The country’s worst heat of up to 46°C is forecast for Phoenix, Arizona, which has seen a record-breaking three weeks in a row of highs above 43°C. There were hellish scenes in the city on Thursday when a fierce blaze erupted at a propane business near the international airport, sending tanks exploding into the air.

“Unfortunately, on a hot day like this, these propane tanks with that expansion of heat, they literally become missiles… They can travel upwards of 500 yards,” Fire Captain Rob McDade told KPHO television station.

Tourists, meanwhile, have been flocking to Death Valley National Park, which straddles the border between California and Nevada, in order to post selfies with a temperature display outside the visitor center.

Meanwhile, Four people in Canada, including two children, have been reported missing in flooding caused by torrential rains in Nova Scotia, police have said.

Officials say the heaviest rains to hit the Atlantic region in 50 years have triggered floods that have left thousands of homes without electricity.

Three months of rain fell in just 24 hours in some areas. Residents have been urged not to join in searches for the missing due to the dangerous conditions.

The two missing children were in a car that was submerged by flood waters, police reported. The three other people in the car managed to escape.

A man and a young person are also missing after the vehicle they were in was also submerged. Two people were rescued from the vehicle.

Roads have been washed away and bridges have been weakened in Nova Scotia, where a state of emergency has been announced in some areas.

“We have a scary, significant situation,” said Nova Scotia Premier Tim Houston, adding that at least seven bridges would have to be replaced or rebuilt.

“The property damage to homes … is pretty unimaginable,” he told a news conference. He estimated that is could take several days for the waters to recede. More than 80,000 people were left without power at one point.