Western Europe is enduring a ferocious heatwave forecast to break temperature records, with half of France on red alert, rail services in Belgium disrupted and sports events in Spain and Germany cancelled or postponed.

French authorities on Monday placed 49 of the country’s 96 mainland departments on a level 1 danger-to-life warning, urging 35 million people to exercise “absolute vigilance”, drink water often, avoid all strenuous exertion and avoid direct sun.

Another 40 departments were on a level 2 orange alert. “Very high temperatures are setting in for the long term across the country,” the national meteorological service, Météo-France, said. “Day and night-time temperatures will be exceptional.”

It said temperatures throughout western and central France were likely to exceed 40C from Monday afternoon, hitting 43C in Bordeaux, 41C in Limoges, 40C in Toulouse and Tours and 39C in Paris, and would continue rising until the end of the week.

Night-time lows are also forecast to be far higher than normal for the season until at least Friday, Météo-France said, with the minimum temperatures recorded in several towns and cities overnight on Sunday already setting all-time records.

France’s national heat index, an average of the day and night-time highs measured at 30 weather stations around the country, is expected to hit its highest ever level on Monday or Tuesday, the forecaster said.

“Many people are going to suffer, because bodies suffer from an accumulation of high temperatures,” said Stéphanie Rist, France’s health minister, visiting a Paris hospital on Monday. She urged people to check on elderly and vulnerable neighbours.

In the south-west Gironde region, local officials said the deaths on Sunday of three people, aged between 80 and 95, were in part due to the intense heat. Emergency services said 10 people, including a 13-year-old boy, drowned in swimming accidents.

France went ahead with its annual street music festival, the Fête de la Musique, on Sunday, although some local authorities called it off altogether and others ran only evening events. Alcohol restrictions were imposed in many areas.

More than 800 schools were closed nationwide on Monday, while another 1,800 rescheduled classes to allow pupils to leave early. One in 10 regional train services around Paris were cancelled amid fears for rolling stock and tracks.

Spain declared its first official heatwave of the year from Sunday until Wednesday, with temperatures forecast to reach 44C in some areas. A public screening in Madrid of the national football team’s World Cup match against Saudi Arabia was cancelled.

The state weather service, Aemet, warned on Sunday of “extremely high” day and night temperatures for the season. “Temperatures will start to drop on Thursday, but the heat will remain intense,” the agency added.

In Germany, organisers suspended the final of the Berlin Open tennis tournament and cleared everyone out of the event location because of severe thunderstorms as temperatures in the German capital topped 30C over the weekend.

Temperatures in Belgium – already past 30C on Sunday – would be “the hottest ever recorded”, David Dehenauw, head of forecasting at the IRM weather institute, said. Some rush-hour trains were cancelled to limit the risk of breakdowns.

In the UK, the weather office has issued an “extreme heat” warning for much of southern England and parts of Wales from Monday until Thursday, predicting temperatures of 38C. The current record for a June day is 35.6 C, set in 1976.

Scientists have said that as Earth continues to warm, extreme heat events historically confined to high summer will become more frequent, more intense and last longer, as well as happening earlier and later in the year.