Recent (1981–2024) climatic trends in Italy from high-resolution reanalysis data and station-based observations

Abstract Extreme heat is among the most severe climate-related risks affecting Europe, with particularly pronounced impacts in the Mediterranean region, where temperatures are increasing faster than the global average. In recent decades, the frequency and severity of heatwaves (HWs) have intensified, leading to substantial societal and environmental impacts, including increased heat-related mortality. In this study, we provide a comprehensive assessment of recent climatic trends in Italy over 1981–2024, focusing on daily temperature extremes, HWs, and standard climate and heat stress (HS) indicators. The analysis integrates the VHR-REA_IT climate reanalysis dataset (∼ 2.2 km) with ground-based observations from the synoptic network of the Italian Air Force Meteorological Service. Trends are estimated using linear regression and analysed across multiple ecoregions and elevation ranges. Results reveal a clear and spatially coherent warming signal across Italy, characterised by increasing warm extremes, particularly in the frequency of tropical nights (up to + 7 days/decade), a marked rise in HW frequency (+ 2 events/decade), and a widespread reduction in cold extremes. The HS analysis further highlights a growing frequency of thermal discomfort conditions during the warm season, including nighttime periods (up to + 8 days/decade), with the strongest increases occurring in lowland and densely populated areas. These findings demonstrate the added value of very high-resolution reanalysis data for tracking spatial patterns in climate trends and provide a valuable basis for stakeholders to support climate adaptation and heat-risk management strategies in Italy under current and future climate change.