A sustained spell of dangerous heat was impacting the lives of millions of people across three continents on Wednesday as fires raged and health worries mounted.

Greece was battling wildfires that have been exacerbated by scorching weather and temperature records have been broken repeatedly in the United States, Europe and China.

Experts have said climate change, driven by the burning of fossil fuels, has played a key role in worsening destructive weather like the current extreme temperatures.

The exceptional heat has prompted safety warnings, with France on Wednesday saying temperatures of up 40 degrees Celsius were expected in parts of the nation’s south.

Two forest fires, fanned by strong winds, were raging to the west of Athens, while another broke out on the tourist island of Rhodes — forcing locals to make painful decisions on whether to flee.

Beijing broke a 23-year-old record with 27 consecutive days of temperatures above 35 degrees Celsius (95 Fahrenheit), forecasters said.