The fact that the days are now shorter than the nights is not evident from the current temperatures in Austria. In many places there are still no traces of colored trees; the foliage is as green as in summer. Some lakes such as Lake Wörthersee, Lake Mondsee and the Old Danube are still attractive for swimming with water temperatures around 20 degrees. But autumn is already on the calendar, the weather is still set for late summer.
According to an analysis by GeoSphere Austria, September 2023 will be the hottest in the 257-year history of measurements in Austria. It was exceptional in every way, an impeccable summer month as it was warmer than the average June. The deviation from the average for the years 1991 to 2020 is 3.3 degrees in the lowlands; In the mountains the difference is even greater, more than four degrees. From a climatological point of view, September is reaching new dimensions.
Previous record from 1810
The hottest September to date was in the distant year 1810, with a deviation of 2.8 degrees from the long-term average. At that time, Francis I ruled the Austrian Empire, his daughter Maria Luise married Napoleon Bonaparte that year, Tyrolean freedom fighter Andreas Hofer was executed, and in September 1810 Salzburg came under Bavarian rule.
GeoSphere Austria/ORF
The fact that the record has been maintained for so long, despite global warming, is almost a sensation. But only at first glance, because there are other old monthly records that are still kept in Austria. According to GeoSphere Austria, April (1800), May (1811) and August (1807) still show highs from previous centuries. At that time, the measurement network was not comparable to today; there were only a few stations in all of Austria.
Climate
Remains at the end of summer
Old records with expiration dates
Ancient records prove that even in the past it could have been very hot under suitable climatic conditions. However, only once in a while; now there are almost only months that are too hot and there is a clear warming trend that can be attributed to the increase in greenhouse gases. This means that all old records will gradually be broken, estimates Marc Olefs, head of the climate impact research department at GeoSphere Austria. When exactly and in what order is a coincidence. Only last year was the maximum value for October set, which has been in force since 1795.
September is no longer a climate “anomaly”.
The fact that September, of all places, is setting a new monthly record is remarkable, because until a few years ago it was, along with October, the only month in Austria that showed few warming trends in recent decades. September was one of the last bastions of this country that seemed to resist man-made global warming.
APA/Barbara Gindl Bathing days in September
In recent years, however, the picture has begun to change. Since 2016, the month of September in Austria has also warmed significantly. And so, what was once a month of autumn is increasingly becoming an extension of summer, a development that climate scientists have long predicted is now becoming reality.
The exceptionally warm September of 2023 is not a local or regional phenomenon limited to Austria. In Germany and Switzerland, for example, previous highs will be significantly surpassed and, even globally, this September will probably be the hottest yet.
More summer days than ever
The reason for this unique September in Austria was long periods of high pressure weather with subtropical air masses, which were rarely interrupted by fronts with colder air from the Atlantic. This has led to an unprecedented abundance of summer days, i.e. days above 25 degrees. Most capitals broke new records. Eisenstadt, where every day of the month was warmer than the long-term average, has 23 days of summer. Only in Innsbruck and Klagenfurt do old records remain.
The station with the most days above 25 degrees is Langenlebarn, near Tulln in Lower Austria. Taking into account the forecast for Friday and Saturday, there will be 26 days of summer; Never before have so many been recorded at one station in September in Austria. The all-time maximum is 25 days of summer at Silberegg in Carinthia in September 1961.
Climate
With temperatures of up to 32 degrees in Bad Deutsch-Altenburg, a heat wave also occurred in the first half of the month, a phenomenon that only occurs in some Septembers. Innsbruck experienced five consecutive days with temperatures exceeding 30 degrees, and throughout the summer the Tyrolean capital had 38 hot days, which corresponds to an increase of a good 60 percent compared to the long-term average.
Record heat also in the mountains
The extreme heat did not spare the mountains either. In Brenner (Tirol) 27.5 degrees were measured on September 10th, the old monthly record was 26.6 degrees in 2006. There were also in Rudolfshütte and the Sonnblick in Salzburg Tauern, both stations with long series of measurements. In September. On average, in September, the Sonnblick observatory experiences 20 nights of frost, this year there were only five. For glaciers, the month was a disaster at the end of a hot summer, and ice melt is still ongoing.
APA/Barbara Gindl It was also unusually hot during walks
The exceptionally warm September also means that 2023 will likely be one of the hottest years in Austria’s history. “If October, November and December are similar to the average of the last ten years, then 2023 will be one of the three warmest years in Austria’s 257-year measurement history,” says climatologist Alexander Orlik from GeoSphere Austria.
Extremely dry in places
Due to long periods of high pressure, the solar balance in September is above average and the rainfall balance is below average. On average, the sun shone 40% more than normal in Austria. Salzburg, for example, has more hours of sunshine than in an average July, although the day is three hours longer every day.
In contrast, only half the amount of rain recorded in an average September fell. Little will change in this regard, even if there are some rain showers on Saturday. The month was particularly dry in the north of the Waldviertel (Lower Austria), in Lungau (Salzburg) and in parts of Upper Styria. In Zeltweg, with just nine liters per square meter, it rained less than ever since measurements began. It was even drier in Litschau, with just six liters of rain per square meter.
A September for the future
Climate researcher Olefs sees this month of September as an atypical situation, with so many heat records, but also as further proof of how our climate is changing and at what pace the changes are occurring.
Not every September in the coming years will be as hot as this year. There is a natural fluctuation that is determined by weather conditions and other influences. But a September like this year could become the norm by the end of the century if climate protection measures are not significantly strengthened globally.
A consistently summery September could be a tempting prospect for some people. On the other hand, temperature deviations of three to four degrees mean even more extreme heatwaves in the summer months than now and, in winter, a virtual end to snowfall in the lowlands.