Towns in south-west France roasted in “completely extreme” heat in the early hours of Tuesday, with overnight temperatures hitting 26.9C (80.42F).

“It’s very exceptional temperatures – even for the summer, let alone late November,” said Matthieu Sorel, a climatologist at Météo France.

Climate scientists across the country described the night-time heat as “staggering” and “phenomenal” for reaching such highs so late in the year. Météo France could not confirm if it was the highest temperature recorded on a November night because its hourly data only stretched back to about 1990, said Sorel. “But still, it’s huge,” he added.

“From what we can remember, [we have] never seen such temperatures during the night for this time of year.”

Violently hot nights are felt on the French side of the Pyrenees when warm air from north Africa and the Mediterranean comes down the mountains and compresses, heating up even more. The natural phenomenon, known as the Föhn effect, adds to the impact of fossil fuel pollution, which has trapped sunlight and heated the planet 1.3C since preindustrial times.

In Europe, which has warmed about twice as fast as the global average, the shift has melted glaciers and dried out reservoirs. It has forced people to suffer through deadly heatwaves that reach catastrophic highs in the day and provide little respite at night.

Temperatures near Pau reached 26.9C at 4am on Tuesday, according to Météo France, and in Biarritz and Tarbes it hit 24C.

The weather agency said it was an exceptional temperature for the end of November, and was higher than the 26.2C recorded on 27 November 1970. It did not break records for the highest minimum temperature, which is measured over a 24-hour period, because a later shift in winds brought cold air from the oceans that pulled temperatures back down.

“What we can see is [that] with climate change, we have way higher temperatures than before for the same meteorological events,” said Sorel.

Media reports suggested that Denmark had experienced its warmest November night on Monday but the Danish Meteorological Institute (DMI) said no records had been broken.

“However, it was a very warm night,” said Herdis Preil Damberg from the DMI. “As a meteorologist, I would explain it by the deep storm low called Bert, located near the UK, which has been generating a strong wind.”

The North Atlantic was also warmer than normal, he added.

Hot nights stress the body and stop people from sleeping. The number of tropical nights with temperatures above 20C – which can prove deadly for older people and those fighting off illness – has doubled or even tripled in most parts of southern Europe.

The European Environment Agency estimates the region may experience up to 100 tropical nights a year by the end of the century under the most extreme global heating scenarios.

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