People pose by a fountain at the Trocadero Place in Paris, France, July 25, 2019. (Xinhua/Gao Jing)

PARIS, July 25 (Xinhua) -- Paris broke all-time high mercury on Thursday afternoon as intense heatwaves triggered red alert, Meteo France said.

The French capital has just broken its absolute heat record, registering 42.6 degrees Celsius at 16:30 local time in Paris-Montsouris, said the country's meteorological services.

Meteo France revealed that for much of the northern cities, including Calais, Lille, Amiens, records for temperatures were broken as the mercury remained high, even during the night.

In Paris, the previous record for July stood at 40.4 degrees Celsius in 1947.

Thursday is the hottest day of this heatwave episode in the country's northern regions. Earlier, the agency forecasted that in the hottest part of the day, the temperatures under shelter will be between 40 and 42 degrees Celsius, very occasionally 43 degrees in certain districts of the capital.

People cool themselves at a fountain near the Trocadero Place in Paris, France, July 25, 2019. (Xinhua/Gao Jing)

On Wednesday, the national weather center raised the heatwave alert to red in 20 departments, the highest alert on the agency's four-scale system.

As hot spell is still engulfing 90 percent of French territory, the warning will be maintained till Friday afternoon as the mercury is set to continue climbing in the zones concerned due to persistent hot and dry air.

Some 60 regions remained on heatwave orange alert till Friday.

"It has never happened. At this level of temperature, one has to be very careful," Prime Minister Edouard Philippe said, adding "With a heat of such intensity... we call for extreme vigilance."

People are recommended to stay indoors, keep cool and drink at least 1.5 liters of water a day to prevent heatstroke.

Authorities have activated a level-three heatwave action plan which involves setting up "cool rooms" in municipal buildings, opening pools for late-night swimming and offering access to garden parks by nightfall to help people cool off.

Tourists walk at the Seine River bank in Paris, France, July 25, 2019. (Xinhua/Gao Jing)

At the end of June, an unseasonably hot weather brought record-breaking temperatures to most French regions.

In the southern city of Gallargues-le-Montueux, temperatures reached 46 degrees Celsius -- the highest on record. It was nearly two degrees above the previous high of 44.1 degrees recorded in August 2003.

France, where temperature average stands at 19.9 degrees for the June-August period, is witnessing "more intense and more frequent heatwaves" due to climate change, warned Meteo France.

To French climate scientist Valerie Masson-Delmotte, the frequency of heatwaves would double by 2050 unless concrete and urgent acts are taken to fight global warming.

"If global greenhouse emissions fall sharply by 2050, there will be stabilisation. Otherwise: (there will be) very long episodes of intense heatwaves between May and October," she wrote on Twitter.

In 2003, a heatwave that lasted two weeks caused the death of some 15,000 people in France and some 35,000 people died across Europe.