Retrospective analysis of the trends in outdoor ambient temperature at Austrian rehabilitation facility sites from 1995 to 2024

Background: Climate change increasingly alters environmental conditions. Heat phenomena negatively impact human health, because heat stress increases heat strain in vulnerable populations such as cardiovascular rehabilitation patients and potentially affects rehabilitation procedures and outcomes.Objective: The RehabHeat study investigates the spatiotemporal patterns of minimum and maximum ambient outdoor temperatures at rehabilitation facilities across Austria over the past three decades. The focus is on seasonal variations and extreme heat events to enable an informed discussion of potential implications for rehabilitation practices.Methods: Temperature data from 64 selected rehabilitation facilities in Austria were analyzed, particularly focusing on Kyselý days (≥3-day periods with maximum temperatures >30.0 °C), Tropical nights, and seasonal temperature trends. Spatial clustering was used to identify regional differences in thermal trends, and temporal patterns were assessed on a 10-year basis, also considering seasonal fluctuations.Results: The analysis revealed a considerable increase in temperature extremes, particularly in Austria's eastern regions, with significant rises in both Kyselý days and Tropical nights. 2019, 2023, and 2024 rank among the hottest years within the past three decades, underscoring an intensifying climatic trend. Seasonal analysis revealed that winter temperatures (average increase in daily maximum air temperature from Decade 1 to 3: 1.93 °C) have risen to a magnitude similar to summer warming (1.92 °C). Autumns were characterized by a protracted transitional phase (1.64 °C), whereas spring exhibited the weakest warming (0.79 °C).Conclusions: Austria's changing thermal landscape, marked by increasing heat extremes and seasonal shifts, challenges to rehabilitation sites. Adaptation measures seem urgently warranted to mitigate health risks, particularly in vulnerable patients and high-burden regions.