PARIS — France gritted its teeth Monday for a week of record-busting temperatures, sweltering in a heat wave combining daytime highs above 104 degrees Fahrenheit and sleep-robbing sweaty nights.

The national weather service, Meteo France, said most of the country — the largest in the European Union — is entering unrelenting conditions that aren’t forecast to ease before Friday.

Meteo France called the heat wave exceptionally intense, “similar to the August 2003 heat wave, but with a still uncertain duration.” France introduced a heat watch warning system after that heat wave, when the highest temperatures in over half a century caused an estimated 15,000 deaths, many of older people in apartments and retirement homes without air conditioning.

Europe is the world’s fastest-warming continent, with temperatures increasing at twice the speed as the global average since the 1980s, according to the European Union’s Copernicus Climate Change Service.

Human-caused climate change is tied to increasing extreme weather, and UN climate agency projections say the next five years should shatter more heat records.

A country with little air-conditioning swelters

Multiple towns in western and central France experienced their hottest night ever Sunday to Monday, Meteo France said.

Paris baked through its hottest night for June, not getting below 75.5 F. The French capital broke another June record with 99.9 F recorded Monday afternoon.

The weather service warned of even hotter nights: “This will continue through the end of the week, with heat levels never before recorded across more than three-quarters of the country on Wednesday and Thursday.”

The heat wave worsened air quality in Paris as it causes the formation of ozone that traps pollution. The air quality monitoring agency in the Paris region said pollutants were likely to exceed the recommended threshold.

In a country without widespread air-conditioning, people tried to adapt. Education minister Edouard Geffray said 1,352 schools were closed on Monday due to the heat, while several thousand adjusted their schedules, with students released earlier and classes relocated in air-conditioned rooms.

Deaths are reported in rivers and a parked car

A growing swath of France, spreading on Monday to more than half its regions, was under a “red alert” for heat, with areas forecast to suffer highs past 104 F and nights not dropping below 68 F.

Broadcasts on the Paris transport network urged commuters to hydrate. Medical specialists warned of the potentially deadly combination of drinking alcohol in extreme heat. Authorities cracked down on alcohol consumption in public.

Multiple drownings were reported as people sought relief in rivers, despite warnings about currents and other dangers.

Two children, aged 2 and 4, were found dead on Monday in their family’s car in a parking lot in the southern town of Carpentras, French media reported, quoting the public prosecutor’s office. Government messages warned parents not to leave children unattended in cars.

Heat warnings spread in Europe

In the United Kingdom, the weather office issued a rare “red” weather warning for Wednesday and Thursday, saying temperatures could exceed 99 F in the shade and could rise to 104 F in parts of England and Wales.

The Met Office said extreme temperatures could cause heat-sensitive equipment to fail, including power and mobile phone services.

Over the last four years, more than 200,000 people across Europe died from heat-related causes, and most of those were preventable, the World Health Organization’s Europe office said this month. The above-average temperatures can cause heat exhaustion and life-threatening heat stroke.