Ever Warmer Summers in the Alps

The weather from May to October was characterized by heat phases in June and August, several days with a very high zero-degree boundary, and very contrasting precipitation amounts from month to month, reported Geosphere Austria, the German Weather Service (DWD), and the Federal Office of Meteorology and Climatology MeteoSwiss in the seventh edition of their joint publication series "Alpine Climate - Climate Condition in the Central and Eastern Alps."

After Intense Early Summer Heat Followed Mild Dog Days

After a generally cool May, an extremely hot June followed. Between mid-July and early August, the heat took a break before returning in mid-August. Averaged over the Alpine region of the three countries, the summer half-year was 0.7 to 0.8 degrees Celsius warmer than the climate average from 1991 to 2020. Both in the lowlands and in the highlands, it is the fourth consecutive summer half-year that was too warm compared to the long-term average.

The hot June led to a very low number of frost days (days with a minimum temperature below 0 degrees) in the high Alps; on the Zugspitze (Germany, 2,956 meters above sea level) and at the Sonnblick (Austria, 3,109 meters), there were 70 to 80 percent fewer than the long-term average. However, over the entire summer half-year, the number of frost days in the high mountains was relatively close to the average values of the reference period 1991 to 2020.

Days with a maximum temperature of 25 degrees Celsius and above (summer days) were found to be above average throughout the Alpine region of the three countries. Between 500 and 1,000 meters, there were on average 25 to 30 percent more summer days in the Central Alps than the average of the reference period 1991 to 2020. In altitudes from 1,000 to 1,500 meters, 25 summer days were recorded, almost twice as many as in an average summer half-year.

Alps: Zero-Degree Boundary in Record Range

With climate change, temperatures are rising even in high altitudes. As a result, the freezing level (the altitude at which the temperature drops below 0 degrees Celsius) during the summer months increasingly climbs above 4,000 meters, reaching the area of the highest Alpine peaks. In the summer of 1995, a freezing level above 5,000 meters was measured for the first time above the Payerne weather station in Switzerland. Since 2022, this has occurred one to four times each year. The highest freezing level was recorded on July 25, 2022, at 5,184 meters. This year, the freezing level reached a new monthly record of 5,125 meters in June.

If the freezing level continues to rise in the summer due to climate change, it will affect various areas, experts concluded. These include water supply, tourism, fauna, and flora. In Switzerland, the freezing level has already risen by 400 to 500 meters since the pre-industrial reference period from 1871 to 1900, depending on the season, and today in the summer, it is approximately at the height of the Jungfraujoch (3,467 meters). Depending on the extent of climate change, the freezing level will continue to rise significantly in the future. In a world that is three degrees warmer compared to the pre-industrial reference period, the average freezing level in the summer would exceed most Alpine peaks.

Contrasting Precipitation Amounts in June and July

Considering the precipitation amounts over the entire summer half-year of 2025, they were average in many regions of the Central and Eastern Alps. However, looking at individual months, there were significant differences, with June and July showing the most striking contrasts and locally setting new records.

June was generally low in precipitation, and the number of precipitation days (days with at least one millimeter of precipitation) was also low. At the Zugspitze, there was even a new negative record: with eight precipitation days in June compared to the average of 17, it was particularly few. In contrast, in July, many stations recorded an above-average number of precipitation days, with Zell am See setting a new record with 25 days.

(APA/Red.)

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