Europeans have already been struggling with the heat this summer, but meteorologists warn that it's going to get even hotter over the next few days.

Widespread alerts warning of medium or high temperatures have been issued across many countries in Western, Central and even northeastern Europe.

Weather forecasters in the UK say the country will sizzle this week in a heat wave that could set a new record for hottest day. Temperatures will peak on Thursday, when the mercury could reach a sweltering 39 Celsius (102.2 Fahrenheit), according to the UK's national weather service, the Met Office.

The hottest temperature ever recorded in the UK is 38.5 C (101.3 F), recorded in Faversham, south east England, in August 2003, according to the Met Office.

Predictions of the hottest day on record come as UK academics call for heat waves to be given names, to ensure the associated dangers are conveyed clearly to the public.

"The Met Office must do more to warn people about the dangers of heat waves and should give names to heat waves the way it does for winter storms," the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science said Tuesday.

The institute cited data from Public Health England to highlight an estimated 863 "excess deaths" as a result of three heat wave events last summer, which was the hottest on record in England.

"Far more people in the UK have died from recent heat waves than from storms, so it should be uncontroversial to start applying names to both," said Bob Ward, the institute's director of policy.

He added: "The Government and its agencies, including the Met Office, must lead the way in communicating the growing dangers of heat waves and other impacts of climate change, so that the British public are better informed and can protect themselves."

"If the Government does not lead on this issue, it also risks encouraging the media to continue to underplay these risks in their coverage, and there will continue to be preventable deaths," Ward cautioned.

Amid the rising temperatures, London's Metropolitan Police said Wednesday that it had recovered the body of a man who had vanished while swimming with friends in the River Thames in London on Tuesday. Searches were continuing Wednesday for two others who disappeared from sight in other parts of the Thames while swimming Tuesday evening.

Over in France, it's set to be even hotter, with meteorologists predicting the heat wave to reach its peak Thursday, with temperatures of 42 C (107.6 F) expected in Paris. On Tuesday, temperatures reached at 41.2 C in the southwestern city of Bordeaux, a record for the city.

In preparation for the intense heat, the national weather service, Météo France, put 80 of its 96 regions on high alert.

A red alert -- the highest level -- has been issued in 20 of the divisions; the other 60 are currently on an orange alert -- the second-highest warning level.

"We wanted to alert everyone, and no one is without risk," French Minister of Health Agnès Buzyn said. "Common sense must prevail, everyone must feel assured by the red level that this will affect all 20 regions. It is a health alert for all citizens."

Buzyn said the government is also encouraging businesses to allow staff to work from home during the heat wave.

French Sports Minister Roxana Maracineanu earlier called for awareness of the high risk of drowning. More than 40 drowning deaths were registered during the week of the first heatwave peak at the end of June -- an unusually high number "closely related to heat waves."

The extreme heat also forced the EDF electricity company to shut down two nuclear reactors in southwest France after they exceeded the heat threshold, according to a company spokesperson.

"We do very thorough studies for the environment and we do not want to damage the fauna and flora. It is a precautionary principle," an EDF spokesperson said. "There are large margins to avoid risk."

France recorded its highest-ever temperature earlier this year on June 29, with a sweltering 45.9°C (114.62 F) in Gallargues-le-Montueux in the southern department of Gard.

Notre Dame's chief architect told Reuters on Wednesday that the record-breaking heat wave could jeopardize the cathedral's vaulted ceiling, which was ravaged by a fire in April.

Meanwhile in Italy, the country's Health Ministry put 15 zones on high alert as Europe battles its second extreme heat wave of the summer.

"The heat here today is not historic. We expect the heat to remain stable until this Friday and heat is expected to increase a bit," a spokesperson from Italy's weather service said, "(On) Saturday and Sunday it is expected to cool down."

Further north, Belgium endured its hottest day ever, with temperatures rising to 102°F (39.2°C), the highest ever recorded in the country, according to the national weather service. The record-breaking temperature was reported in Diepenbeek, in the eastern province of Limburg.

The World Meteorological Organization defines a heat wave as a period when temperatures are at least 5 C above average for five consecutive days.