Record Heat in Austria: 66 Stations with New Annual Records, 39.7 Degrees at Hohe Warte

Particularly striking were the readings in Vienna. At Hohe Warte, where daily maximum temperatures have been recorded since 1872, the previous June record of 36.1 degrees from 1950 was exceeded by 3.6 degrees. The annual record of 38.5 degrees from August 2013 was also significantly lower than the new peak of 39.7 degrees. In total, 157 of 277 weather stations set new records for absolute maximum temperature for the month of June.

Records in the High Mountains

The new records differed markedly from previous peak values. At 46 stations, the June maxima surpassed the previous highs by two degrees or more; on average, the new temperature maxima were 1.4 degrees above the previous best marks. Orlik stressed: „Das bemerkenswerte an den neuen Juni-Rekorden ist, dass sie die alten nicht um ein paar wenige Zehntel Grad überboten haben."

The heatwave also reached an unprecedented extent in the high Alps. At Hoher Sonnblick at 3,109 meters above sea level, the mean of daily maxima during the heatwave was ten degrees and that of daily minima was 4.5 degrees – both new highs in the measurement history of the observatory, where June values have been recorded since 1887. Orlik explained: „Für die zweite Junihälfte lag die Lufttemperatur rund fünf Grad über dem Klimamittel 1991-2020 und gar sieben Grad über dem wesentlich kälteren Klimamittel 1961-1990."

Tropical Nights of Previously Unseen Extent

The burden went far beyond individual hot days. Depending on the region, there were ten to 14 consecutive hot days below 800 meters above sea level – days with temperatures of at least 30 degrees. Orlik underscored: „Das belastende in dieser extrem heißen Phase im Juni waren aber nicht nur Tageshöchstwerte von bis zu 40 Grad, es war auch die Länge der Hitzewelle, die ganz Österreich erfasst hatte."

Nor did the nights offer much relief. In the night of 28 to 29 June, the air temperature at 94 GeoSphere Austria weather stations did not fall below 20 degrees – the greatest extent of tropical nights ever measured in Austria. Comparable nights with such a widespread occurrence of tropical nights had previously only occurred on 4 August 2017 and 30 June 2024. At Vienna's Jubiläumswarte (450 meters above sea level), the minimum air temperature during the night of 29 June reached only 27.3 degrees; the previous record for the warmest night was 26.9 degrees, set on 2 August 2017.

The first tropical nights occurred sporadically on 17 June; by 22 June, 35 weather stations already recorded tropical nights. A daily maximum of 38 degrees was reached at 46 stations and 39 degrees or more at 15 stations. Orlik concluded: „Solche Verhältnisse traten im bundesweiten Ausmaß in einem Juni noch nicht auf."

Longer-Term Trend and End of the Heatwave

The data fit into a longer-term trend. A trend analysis of the longest heatwaves in the provincial capitals shows that the strongest heatwaves in today's climate last on average around seven days longer than around 1960 – an increase of approximately 140 percent. Comprehensive evaluations using the SPARTACUS dataset show for the period 2016 to 2025 compared to 1961 to 1990 a clear increase in extreme hot days with at least 35 degrees and in tropical nights with no less than 20 degrees, particularly in the eastern lowlands and at low elevations in the west.

The heatwave gradually subsided toward the end of the month. The series of hot days ended in Vorarlberg, Tyrol, Salzburg and Upper Austria on Tuesday, 30 June. In Lower Austria, Vienna, Burgenland, Styria and Carinthia, the 30-degree mark was exceeded at least in some parts of the country once again on Wednesday, 1 July.