The Complexity Science Hub’s interactive heat map has been updated with data through August 1, 2026. The new data show that extreme heat is increasingly affecting regions in western Austria as well. And already, 22 Austrian districts are dealing with a very high heat stress index.
The updated data come amid a summer of extreme heat across much of Europe. On August 4 and 5, 2026, Austria’s all-time heat record was broken twice in a row (most recently 41.2 °C in Bad Deutsch-Altenburg), after the 40-degree mark had already been reached in June and July – making 2026 the first year in which the 40-degree mark was reached in all three summer months.
Across Europe, several severe heatwaves have occurred since May 2026, with records reported in countries including Germany and Poland. Estimates by the Robert Koch Institute put the number of heat-related deaths in Germany alone at 11,900 by the end of July. Heat is already among the deadliest weather-related hazards in Europe.
“Heatwaves are becoming more frequent and pose a significant health burden, particularly for older people. Between 2015 and 2022, each additional heat day (above 30 °C) increased mortality in Austrian districts by 2.4% per 1,000 inhabitants. If one in four residents in a district is over 65, this effect doubles,” explains Hannah Schuster, researcher at the Complexity Science Hub and WU Vienna.
FIRST INSIGHTS FROM THE 2026 DATA
The current version of the CSH Heat Map already includes data from January through July 2026. Since August, and to some extent September, are among the warmer months of the year, the figures – and consequently the colors of municipalities and districts – may still change significantly by the end of summer. The data available so far nevertheless provide an initial picture and reveal clear trends.
The CSH Heat Map shows two different indices:
- Heat Index: Takes into account only the number of heat days (above 30 °C), showing where exceptionally high numbers of heat days occur.
- Heat Stress Index: Combines the number of heat days (above 30 °C) with the share of the population aged over 65, showing where the health burden is particularly high.
Heat Index – First Insights from 2026
- Western Austria also strongly affected: While previous years have primarily seen high heat exposure in eastern Austria, western regions are also experiencing high numbers of heat days in 2026. Municipalities in the districts of Dornbirn and Feldkirch, for example, have already recorded an average of 34 heat days, followed by Innsbruck and Bludenz with 30. By comparison, Vienna recorded 32 heat days.
- Top 3 municipalities all in Carinthia (well, actually Top 10): With 39 heat days each, Ebenthal, Feistritz, Ferlach and seven other Carinthian municipalities recorded the highest number of heat days as of August 1.
- Reutte has the fewest heat days: With an average of just under 10 heat days, Reutte remains Austria’s coolest district – as it has in previous years.
- Vienna again leads in tropical nights (never below 20 °C): Eight Vienna districts (1st, 2nd, 4th, 5th, 6th, 7th, 8th and 9th) have already recorded 30 tropical nights each, the highest number in the country. In the other provincial capitals, the figure is in the single digits – with the exceptions of Eisenstadt, with 15, and Linz, with 11 tropical nights.
- Only 548 municipalities have so far had no tropical nights: This means the number of municipalities spared tropical nights in 2026 is already lower than ever before. By comparison, there were 1,207 such municipalities in the cooler year 2025 and 1,890 in 2020.
- Heat days and tropical nights are occurring at higher temperatures overall: Temperatures measured on heat days and during tropical nights in 2026 so far are higher than in previous years – including the record years 2024 and 2003 (see figure; the orange line marks the median).
Heat Stress Index – First Insights from 2026
- Very high heat stress index already in 22 Austrian districts and 373 municipalities: In these districts and municipalities, more than 22.8% of the population is aged over 65, and at least 28 heat days had been recorded by August 1, 2026.
- Carinthia, Burgenland and Lower Austria particularly affected: Based on the share of the population aged over 65, these federal states face a particularly high potential health risk. In absolute numbers, Vienna has the largest population aged over 65.
- Only one district – Reutte – still has a low heat stress index in 2026: Reutte has recorded 9.6 heat days on average and has a share of 22.5% of residents aged over 65.
- The east-west divide remains pronounced: The heat stress index is still significantly higher in eastern Austria in 2026. Western federal states, particularly Vorarlberg but also Tyrol, are recording significantly more heat days than in previous years. However, the share of older people is lower in these regions.
“We are seeing more and more extremes: this year, temperatures exceeded 32°C on around half of all heat days,” says Hannah Schuster. “The number and intensity of tropical nights are also increasing. Of course, there are still years with relatively few tropical nights, but looking at the period from 2018 to 2026, only two years recorded relatively few tropical nights.”
Urban areas are particularly affected, the researcher says. Measures such as structural changes and greening can naturally help to mitigate the effects to some extent. “It is also important to provide people in areas with many heat days with opportunities to cool down. Easily accessible places such as air-conditioned rooms can provide relief. Medical facilities such as hospitals and nursing homes should also be taken into account, as they are home to particularly large numbers of vulnerable people. Schools should also be included in heat protection plans, as periods of heat are starting earlier and earlier. This year, we already experienced a heatwave in June,” Schuster emphasizes.
About this research
The interactive Heat Map of the Complexity Science Hub, “Heat, Health and Habitats,” is available here. Further information on the Heat Map is available here.
The study “Heat, health, and habitats: analyzing the intersecting risks of climate and demographic shifts in Austrian districts” has been published in Scientific Reports in 2025.
