Extreme rainfall reshapes permafrost thermal regimes across the Northern Hemisphere

Extreme rainfall can alter thermal and hydrological dynamics of the active layer in permafrost regions, potentially accelerating thaw and climate feedbacks, yet the specific controls on soil temperature responses remain unclear. We combined four extreme rainfall indices with three analytical approaches to assess impacts at 131 Northern Hemisphere permafrost sites, and used principal component analysis to identify soil thermal responses patterns. Results show extreme rainfall cools shallow soils but warms deeper layers. Additionally, extreme rainfall cools permafrost in humid regions, disturbed land surfaces, and areas with low ground ice and soil organic matter. In contrast, precipitation warms permafrost in arid regions, shrub-dominated landscapes, and where ground ice and organic matter are high. These patterns indicate that extreme rainfall is a major driver of permafrost change and can accelerate active-layer thaw. Because response direction and magnitude depend on regional climate and ecosystem characteristics, future climate projections must explicitly include rainfall extremes.