MILAN (AP) _ Officials warned residents and tourists packing Mediterranean destinations on Tuesday to stay indoors during the hottest hours as the second heat wave in as many weeks hits the region and Greece, Spain and Switzerland battled wildfires.

In Italy, Red Cross teams checked on the elderly by phone while in Portugal they took to social media to warn people not to leave pets or children in parked cars. In Greece, volunteers handed out drinking water, and in Spain they reminded people to protect themselves from breathing in smoke from fires.

Several parts of southern Europe are sweating through a new heat wave, amplified by climate change, that is expected to persist for days. The U.N. weather agency said that temperatures in Europe could break the 48.8-degree Celsius (119.8-degree Fahrenheit) record set in Sicily two years ago, as concerns grew the heat would provoke a spike in deaths.

In Cyprus, health authorities confirmed that a 90-year-old man died over the weekend from heatstroke while six other elderly people have been hospitalized. All seven suffered heatstroke at home last week as temperatures surpassed 43 degrees Celsius (110 degrees Fahrenheit).

“Heat waves are really an invisible killer,” Panu Saaristo, emergency health unit team leader for the International Federation of Red Cross and Red Crescent Societies, told a briefing in Geneva. “We are experiencing hotter and hotter temperatures for longer stretches of time every single summer here in Europe.”

Heat records are being shattered all over the world, and scientists say there is a good chance that 2023 will go down as the hottest year on record, with measurements going back to the middle of the 19th century.

June saw the warmest global average temperature, according to Europe’s Copernicus Climate Change Service, and the U.N.’s World Meteorological Organization predicted that a number of heatrecords were set to fall this summer. The global organization said unprecedented sea surface temperatures and low Arctic sea-ice levels were largely to blame.

Human-caused climate change from the burning of coal, oil and natural gas is making the world hotter and is being amplified by the naturally occurring El Nino weather phenomenon. But the current El Nino only started a few months ago and is still weak to moderate and isn’t expected to peak until winter.

Temperatures above 40 degrees Celsius (104 degrees Fahrenheit) were forecast to persist not only in the Mediterranean, but across North America, Asia and North Africa.

In Italy, health officials warned of extreme temperatures in 20 cities, rising to 23 on Wednesday, from Bolzano in the north to Palermo in the south.

In Greece, where a second heat wave is expected to hit Thursday, three large wildfires burned outside Athens for a second day. Thousands of people evacuated from coastal areas south of the capital returned to their homes Tuesday when a fire finally receded after they spent the night on beaches, hotels and public facilities.

But wildfires continued to burn out of control to the north and west of Athens.

Authorities last week introduced changes in working hours and ordered afternoon closures of the Acropolis and other ancient sites to allow workers to cope with the high heat. Temperatures ashigh as 44 C (111 F) are expected in parts of central and southern Greece by the end of the week.

Most of Spain is under alert for high to extreme heat with forecasts calling for peak temperatures of 43 C (109 F) in areas along the Ebro River in the northeast and on the island of Mallorca. Spain is also dealing with a prolonged drought that has increased concerns about the risk of wildfires.

Some 400 firefighters assisted by nine water-dumping aircraft labored to extinguish a wildfire that burned for a fourth consecutive day on La Palma in Spain’s Canary Islands. Authorities said that a perimeter has been established around the blaze but that it is still active.

In Switzerland, some 150 firefighters, police, troops and other emergency teams backed by helicopters fanned out Tuesday to fight a wildfire that engulfed a mountainside in the southwestern Wallis region, evacuating residents of four villages and hamlets in the area.

In a report Monday, the U.N. weather agency said that a committee of experts has verified the accuracy of the 48.8 degree Celsius record set on August 11, 2021, in Sicily. A full report has not yet been published.

The previous verified record of 48 degrees Celsius (118.4 degrees Fahrenheit) was set in Athens on July 10, 1977.

“These are not your normal weather systems of the past. They have arrived as a consequence of climate change,” said John Nairn, senior extreme heat adviser for WMO. “It is global warming, and it’s going to continue for some time.”

Nairn noted a sixfold increase in simultaneous heat waves since the 1980s, “and the trend line isn’t changing.”