Bregenz and Graz lead Austria’s capitals in heat days

Bregenz and Graz have recorded the most heat days among Austria’s state capitals so far this year, according to ORF, citing updated data from the Complexity Science Hub. Heat stress has increased across the country, including in Vorarlberg.

In 2018, about one quarter of Austrian municipalities experienced high or very high heat stress. In the first half of 2026, the figure had risen to more than half.

According to GeoSphere Austria, the low-lying areas of Vorarlberg, including Bregenz, Dornbirn and Feldkirch, are among the western lowlands where heat stress has increased particularly sharply.

Bregenz recorded its first heat day of the year on June 17, when temperatures exceeded 30 degrees Celsius. The heatwave continued until the end of June. Municipalities below 800 metres recorded between 10 and 14 consecutive heat days, including many heavily populated communities in the Rhine Valley.

Tropical nights add to health burden

The number of heat days in Bregenz has risen significantly compared with previous climate periods. Heat days were rare between 1961 and 1990 and increased moderately between 1991 and 2020. A sharp rise has been recorded from 2020 through 2025 and into 2026.

Tropical nights, when temperatures do not fall below 20 degrees Celsius, are also placing pressure on health. GeoSphere Austria said the increase has been particularly pronounced in the eastern lowlands and the western low-lying areas. Tropical nights were recorded at 94 weather stations across Austria on the night of June 28 to 29, marking a preliminary peak of the heatwave.

Lech records no heat days

While temperatures in the valleys rose above 30 degrees, Lech in the Arlberg region avoided classic heat days. The municipality, at around 1,400 metres above sea level, recorded none so far this year. Together with Innervillgraten in Tyrol, it was one of only two municipalities in Austria without such extreme temperatures.

Even in the high mountains, however, temperatures were well above average. GeoSphere Austria said air temperatures in the second half of June were around five degrees above the 1991 to 2020 climate average and seven degrees above the 1961 to 1990 average.

The current heatwave is consistent with the long-term trend towards more extreme heat linked to climate change. Alexander Orlik, a climatologist at GeoSphere Austria, said the strongest heatwaves now last an average of around seven days longer than they did around 1960, an increase of about 140 percent.

Nationwide assessments using the SPARTACUS dataset show a clear increase in extreme heat days and tropical nights, particularly in the eastern lowlands and western low-lying areas.

The figures could still change significantly before the end of summer because August, and to some extent September, are among the warmer months of the year, the Complexity Science Hub said. The data available so far nevertheless show clear trends.