It will soon be difficult to seek freshness at altitude. The heat wave, which has been hitting southern Europe since this weekend and which is expected to intensify further on Tuesday, is also raging in the mountains. As proof, the Swiss weather forecast has announced that it has recorded an absolute altitude record for the zero degree isotherm. This is the altitude at which the temperature becomes negative.
“The Payerne radiosounding this night from August 20 to 21, 2023 measured the 0 ° C isotherm at 5298 m, which is a record since the start of measurements in 1954”, announced on the social network X the federal office . This record erases the previous one which dated from only last year with an altitude of 5184 m to reach the temperature of 0°C recorded on July 25, 2022.
The zero degree isotherm is a meteorological index that is very useful for climatologists to measure in particular the evolution of the climate. It is also used by mountaineers and mountaineers to assess the state of the mountain, from snowpacks to permafrost and glaciers.
In France, the 0°C isotherm is also very high on these days of heat wave around 5000 m altitude. It should stay at this altitude until Wednesday according to La Chaîne Météo* . “Be careful if you plan to hike in the high mountains near the alpine glaciers which will be weakened by these exceptionally high temperatures!”, The organization also specified in a publication.
With a negative temperature from 5000 m only, Mont Blanc (4809 m) therefore experiences positive temperatures, and therefore an exceptional thaw. The temperature record at the top of Europe’s roof is unlikely to be broken, however, according to forecasts. It would indeed be necessary to record a temperature higher than 10.4°C measured on June 18, 2022 at the Italian meteorological station installed at the Col Major (4750 m), very close to the summit.
*The Weather Channel is owned by the Le Figaro group.