One of the warmest summers in recorded history

Preliminary climate assessment by GeoSphere Austria: Austria's lowlands experienced their eighth warmest summer on record, while the mountains experienced their seventh warmest. June and August were significantly too warm, too dry, and too sunny, while July was relatively cool, wet, and cloudy.

The meteorological summer of 2025 (June, July, August) brought large temperature differences. For example, the transition from the third warmest June in recorded history to a relatively cool and wet July was very striking.

“Overall, however, the summer of 2025 brought more periods that were significantly too warm than too cool. In the preliminary assessment, this puts it in eighth place in the list of the warmest summers in Austria's 259-year measurement history in the lowlands and seventh place in the 175-year mountain measurement series,” says climatologist Alexander Orlik from GeoSphere Austria.

Taking into account the forecast for the last days of August, the summer of 2025 will be 1.1 degrees above the average for the climate period from 1991 to 2020 in the lowlands of Austria and 1.4 degrees above average in the mountains. Compared to the 1961-1990 climate period, which was not yet so strongly affected by global warming, the summer of 2025 will be 2.9 degrees above average in the lowlands and 3.1 degrees above average in the mountains.

The summer of 2025 is pretty much in line with the long-term warming trend of recent decades. An average summer is now three degrees warmer than it was 40 years ago.

The 20 warmest summers in the 259-year history of measurements are almost exclusively from the recent past: 2024, 2003, 2019, 2015, 2022, 2017, 2018, 2025, 2023, 1992, 1811, 2021, 2012, 1994, 2013, 1807, 2002, 1834, 2020, 2016 (HISTALP lowland data set).

Although the number of hot days (at least 30 degrees Celsius) was not as extreme as in the summers of 2003, 2015, and 2024, there were still significantly more hot days than in an average summer in the recent past. “At altitudes below 500 meters above sea level, there were an average of 24 hot days in the summer of 2025. That is 50 percent more than in an average summer during the climate period from 1991 to 2020,” says climatologist Alexander Orlik from GeoSphere Austria. “At altitudes of 500 to 1000 meters above sea level, the summer of 2025 brought an average of 16 hot days. That is 90 percent more than the average from 1991 to 2020.”

The number of summer days (at least 25 degrees Celsius) was also well above the average for the recent past: below 500 meters above sea level, there were an average of 62 summer days in the summer of 2025 (+18 percent compared to the climate period 1991-2020). Between 500 and 1000 meters, there were an average of 47 summer days (+25 percent), and at altitudes between 1000 and 1500 meters, there were an average of 29 summer days (+75 percent).

The precipitation balance for the summer of 2025 is slightly too dry. Taking into account the forecast for the last days of August, the Austria-wide evaluation of summer 2025 showed seven percent less precipitation than the long-term average. This balance is made up of a very dry June and August (around a third less rain than average in each month) and a very wet July (+40 percent).

Similar differences can be seen in the analysis of sunshine hours: June was very sunny (+39 percent), July was relatively cloudy (-27 percent), and August was relatively sunny (in the preliminary analysis +14 percent). In the analysis of the entire meteorological summer of 2025, this results in a slightly sunny summer (+8 percent).

Translated with DeepL.com (free version)