Millions across France endured another night of intense heat, waking up in sweltering conditions as a severe heatwave pushed temperatures to extreme and potentially record-breaking levels across much of the country.

France’s national weather agency, Meteo France, placed 54 departments—nearly half the country—under a red heatwave alert, warning that dangerously high temperatures will continue around the clock.

With large parts of France lacking widespread air conditioning, the heatwave has disrupted daily life, forcing changes to school schedules, train services and sporting events. Authorities also reported around 20 drowning deaths since the weekend, as people seek relief in rivers and lakes.

Meteorologists said the hot spell is expected to persist at least through the end of the week, with daytime temperatures rising above 40°C (104°F) in several areas. They warned that some locations could see record-breaking highs for any time of year.

“Sunshine continues to dominate across France, maintaining oppressive and exhausting heat throughout the country,” Meteo France said, adding that the situation remains especially severe due to its early arrival in the summer season.

The current heatwave has drawn comparisons with the deadly August 2003 heatwave, when an estimated 15,000 people died in France, many of them elderly residents in homes without cooling systems. The disaster later led to the introduction of France’s national heat alert system.

Scientists say human-driven climate change is increasing the frequency and intensity of extreme weather events. Europe, in particular, is warming at about twice the global average, according to the European Union’s Copernicus Climate Change Service.

The World Health Organization’s Europe office has warned that more than 200,000 heat-related deaths have occurred across the continent in recent years, many of which could have been prevented. Extreme heat can cause dehydration, heat exhaustion and life-threatening heatstroke.

Meanwhile, neighbouring Britain is also facing severe conditions. The UK Met Office has issued an extreme heat warning for Wednesday and Thursday, with temperatures expected to reach up to 39°C (102°F) in parts of the country. Officials said this month could challenge or break June temperature records before conditions ease later in the week.

Experts warn that rising global temperatures are making heatwaves more frequent and intense, increasing risks of wildfires and serious health impacts across Europe.