GENEVA — Switzerland's heatwave is expected to continue until Thursday, with highs of 37°C.

The Swiss weather service had to climb to a record altitude of almost 5,300 meters to record the zero-degree 'freezing point' — or isotherm — at a time when much of the country is on heatwave alert.

"The radiosonde from Payerne [a weather station in north-western Switzerland] on the night of 20 to 21 August 2023 measured the 0°C isotherm at 5,298 m, which is a record since measurements began in 1954", weather service MétéoSuisse said on Monday morning.

The previous record was set on 25 July last year at 5,184 meters.

Temperature decreases with altitude, and depending on the season and weather conditions, the altitude above which the temperature falls below 0°C varies.

"This surface, known as the zero degree isotherm, separates layers of air with temperatures above 0°C at low altitudes from those below freezing at higher altitudes," explains the weather service on its website.

Because of its major influence on the development of vegetation, snowfall limits and the water cycle, the zero-degree isotherm plays a key role in weather forecasting and in everyday life in the Alpine region.

Switzerland, like much of Europe, is currently experiencing a heatwave, with temperatures exceeding 30°C below 800 meters since Friday.

The heatwave is expected to continue until Thursday, with highs of 37°C. — Euronews