Europe’s Double Threat: Evolving patterns of compound heatwaves and droughts

• Compound hot and dry events (CHDEs) have intensified across Europe since 1980. • Mediterranean regions, especially southern and southeastern Europe, show the strongest trends. • High-severity hotspots are found in Spain, Italy, Greece, Turkey, and Bulgaria. • Extreme CHDEs have become more frequent and longer lasting in recent decades. • Urgent, region-specific adaptation is needed in vulnerable areas. Compound Hot and Dry Events (CHDEs), the co-occurrence of heatwaves (HWs) and dry events (DEs), are intensifying across Europe, heightening risks to human health, agriculture, and ecosystems. This study quantifies the spatiotemporal evolution, frequency, duration, and severity of CHDEs from 1980 to 2023 and identifies both persistent hotspots and emerging risk regions. A compound-event detection framework combining percentile-based HW thresholds (85th, 90th, 95th) with Effective Drought Index (EDI) metrics was applied to E-OBS daily data at 0.1° resolution for the warm season (May–September). Three indicators, frequency, total occurrence, and severity, were used to assess long-term trends and spatial variability. Vector analysis decomposed CHDE drivers, estimating the relative contributions of HWs and DEs. Results show a 35–45% increase in annual CHDEs after 2000, with severe 7-day events (95th percentile) rising by 2.7% per year. The Mediterranean basin (Iberia, southern France, Italy, Greece, western Turkey) remains the principal hotspot, while central and northern Europe (Germany, Poland, the Baltic region, southern Scandinavia) have experienced a three- to five-fold rise in frequency. Vector angles (mean ≈12°) and magnitudes indicate HWs as the dominant driver, with DEs amplifying risks regionally. Urban areas exhibit 60–70% higher growth rates than rural zones, reflecting strong Urban Heat Island effects. These findings highlight two adaptation priorities: (1) enhancing drought–heat resilience in the Mediterranean (MED)through water-efficient agriculture and heat-health preparedness, and (2) strengthening monitoring and early-warning systems in emerging northern hotspots. The study underscores the urgent need for compound-aware, region-specific strategies to safeguard Europe’s food, water, and energy security under future warming scenarios.