Climate‐Dependent Mechanisms Accelerate Flash Droughts in Drylands and Humid Regions

Abstract Flash droughts have drawn increasing attention due to their rapid onset and severe impacts. However, the physical factors controlling onset speed remain poorly understood across climate regimes. This study presents a global assessment of flash drought onset speed using satellite‐based evaporative stress estimates and Shapley Additive Explanation interpretation to identify dominant hydrometeorological factors that govern drought acceleration. We find that while humid regions experience flash droughts more frequently, events in drylands intensify more rapidly. This contrast reflects differences in energy and water constraints: net radiation plays a greater role in humid regions, whereas surface drying dominates in drylands. Moreover, short‐term antecedent moisture recovery followed by rapid drying accelerates the onset, with soil moisture depths and timescales exerting region‐specific influences. These results reveal climate‐dependent mechanisms underlying flash drought intensification and highlight the need for tailored monitoring strategies in diverse hydroclimatic contexts.