Europe is being blasted by an unprecedented heat wave that has seen the highest recorded temperatures in three countries.

Three swimmers were found dead this week in England in the high heat, and one more is missing, while one child died in Austria.

The Netherlands, Germany, and Belgium have seen record-high temperatures, while France and England could see national records broken Thursday, forecast to be the hottest day.

Belgium reached 40.2 degrees Celsius, or 104.4 Fahrenheit, the Netherlands reached 39.3 C (102.74 F), and Germany reached 40.5 C (104.9 F) — and these temperatures could be surpassed still.

The heat wave came just one month after another huge heat wave in the continent, which too saw some countries experience record temperatures for June.

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Europe is battling an unprecedented heat wave that has seen record-high temperatures in three countries and has already been associated with at least four deaths.

The heat is blasting northern and western Europe with temperatures that have already set records in Germany, Belgium, and the Netherlands just one month after another huge heat wave hit the continent.

The Netherlands saw its highest recorded temperature as the city of Eindhoven reached 39.3 degrees Celsius, or 102.74 degrees Fahrenheit. Most of the country is under an orange alert until Saturday, with authorities implementing the country's national heat plan.

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Belgium recorded a record temperature of 40.2 C, or 104.4 F, on Wednesday and said the record could be broken again Thursday. Almost all of the country is on red alert, a status Belgian authorities say is issued only for "extremely high temperatures."

And Germany saw a record temperature of 40.5 C, or 104.9 F, on Wednesday, though it too said Thursday could be hotter. The national meteorological service issued a heat warning for almost all of the country.

The UK and France are also battling extreme heat and could see their national records broken Thursday, which is expected to be the hottest day. Spain and Portugal are also battling wildfires as temperatures rise, and Italy has issued fire alerts.

People cooling off in the Mediterranean Sea in Calella, Spain, on Wednesday. REUTERS/Albert Gea

The UK had recorded its second-hottest temperature ever on Thursday afternoon, at 37.7 C (99.86 F). Forecasters said it could break the England's record high of 38.5 C, or 101.3 F later on Thursday.

London's Metropolitan Police said that it had found the bodies of two men who went swimming in the Thames and that it was still searching for another man who went missing in the river.

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The police also found a body in a water park in Gloucestershire, southwestern England, on Tuesday.

Swimming-related deaths tend to spike in extreme heat as people enter bodies of water — like the Thames — which are rarely used for swimming. The colder water can also put people into shock, leading to their deaths.

The Metropolitan Police warned people on Thursday not to swim in the river, which cuts through London, even though it "may look appealing, especially in this hot weather," as it is "dangerous all year round."

A stretch of the River Thames running through central London. Photo by Tom Shaw/Getty Images

The police in Austria said a 2-year-old boy died after climbing into his family's car without their noticing and overheated, the Associated Press reported. Temperatures in Austria are only 26 degrees Celsius, or 74 Fahrenheit, which is cooler than many European countries this week, but authorities have still warned that children and pets are at risk in cars.

Paris reached 40.6 C, or 105.08 F, on Thursday afternoon — the hottest ever recorded in the city — and forecasters said the temperature was still increasing.

The French city of Bordeaux hit its highest recorded temperature on Tuesday, at 41.2 degrees C, or 106.1 F, and France's emergency services were on high alert as temperatures continued to rise Thursday.

Some French cities, including Paris, have barred some vehicles from their centers in a bid to cut down on pollution.

A child during a heat wave in Vienna on Tuesday. REUTERS/Lisi Niesner

Andreas Friedrich, a spokesman for the German meteorological service DWD, said of the forecast in Germany: "As a meteorologist, I have never seen anything like this before."

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England's public health service told people to "know the steps to take for keeping cool and that you're looking out for those who are more vulnerable in the heat."

The UK Met Office also urged people to look out for vulnerable people, like the elderly, and to keep out of direct sunlight. Train companies have been running reduced services, as they were forced to slow down to prevent railway lines from buckling in the heat.

Luxembourg, Italy, and Sweden are also facing temperatures higher than 30 C, or 86 F.

People in the large pool of the Trocadero fountain overlooking the Eiffel Tower during the heat wave that blasted Paris in June. Samuel Boivin/NurPhoto via Getty Images

The heat comes just one month after a huge heat wave gripped much of the continent, breaking June temperature records in Germany, Poland, and the Czech Republic, giving France its highest recorded temperature, and prompting one Spanish meteorologist to tweet "Hell is coming."

One French village recorded temperatures of 45.1 C, or 113.18 F, and France opened new public pools and parks in a bid to keep people cool and avoid a repeat of a 2003 heat wave was linked to the deaths of 15,000 people in the country.

June ended up being the hottest month on record around the world.

Much of the eastern US was also hit by a heat wave this month.