Temperatures have hit 40C in parts of Europe as storms moved into other areas, with France reporting 1000 excess deaths during the record-breaking heatwave.
The French public health agency said most of the heat-related fatalities involved older people and warned the number was expected to rise as more details became available about deaths in residential care and private homes.
Scientists have said the heatwave, which began on June 20, was the worst recorded in Europe, and the blistering conditions have disrupted power generation, damaged infrastructure and overwhelmed healthcare systems.
"Right now 150 million people are living under extreme heat, hundreds have died, schools are shut, grids are buckling," World Health Organisation director-general Tedros Adhanom Ghebreyesus said on the X platform.
"Driven by climate change and global warming, the phenomenon of the 'once-in-a-generation' heatwave is now occurring nearly annually. We were warned," he wrote, adding that homes, workplaces and schools in European countries were ill-equipped for extreme heat.
Temperatures topped records in Austria, the Czech Republic, Germany and Poland on Sunday while storms broke out in parts of France, causing further disruption to travel and power supplies.
In Germany, train services were reduced on a major rail line in the western state of North Rhine-Westphalia and trams were suspended in the eastern city of Leipzig.
Many people hunkered down at home, reluctant to go outside until the sun went down, local media reported.
In Rome, Pope Leo thanked worshippers for attending Sunday's prayer in Saint Peter's Square despite the sweltering conditions.
The extreme heat has also affected Europe's rivers, depleting and warming their waters, and causing problems for electricity generation and agriculture.
Hungary's Paks nuclear power plant reduced output again on Sunday due to the high temperature of the Danube River that it uses as a coolant, the government said.
In Italy, the flow of the Po has dwindled, allowing seawater to advance as far as 18km inland and raising fears for agriculture and protected wetlands in the river delta.
Dozens of people seeking relief from the heat are reported to have drowned.
In Italy, rescuers were searching for the husband of cabinet minister Eugenia Roccella, who went missing on Saturday while swimming in Lake Vico, 70km from the capital Rome.
Thunderstorms could hit parts of France, Germany and the Czech Republic over the next day or two, with cooler weather forecast in much of western Europe this week as the heatwave moves deeper into central Europe and the Balkans, meteorologists say.
