Asymmetric impacts of precipitation on global extreme humid heatwaves

Extreme humid heatwaves (HS) have emerged as one of the most threatening compound events under climate change. Yet their dynamic evolution and mechanism, especially the relation with antecedent precipitation, remain unclear. Here, we provide a global assessment of HS dynamics using reanalysis data from 1979 to 2024. Results reveal significant intensification trends in HS frequency, duration, and intensity. The occurrences of HS are mainly driven by humidity anomaly in 73.41% of global land areas. The relations between antecedent precipitation and HS are strengthening. HS tends to occur more rapidly after the cessation of long-duration heavy rainfall, mainly due to rapid soil moisture evaporation enhancing near-surface humidity; in contrast, HS following weak or short-duration precipitation exhibit a slower transition and stronger dependence on large-scale high-pressure systems. The distinct patterns demonstrate differentiated regulatory mechanisms of HS across different antecedent precipitation types and necessitating context-specific adaptation strategies tailored to these divergent precipitation-HS relationships.