Divergent patterns of rainfall regimes in dry and humid areas of China

•Rainfall amount and rainy days increased in dry regions and decreased in wet regions.•Wet seasons extend to dry areas and shorten in wet areas, with trends related to dryness.•As the dryness increased, the length, number, and cumulative number of dry days increased.•Seasonal rainfall regime tends to greater variations in drier areas. Monitoring the long-term dynamics of the wet season is important for both the current operation and future management of water resource systems. Wet seasons in China are substantially influenced by monsoons with great variability but are unknown. We conducted a comprehensive assessment of rainfall regimes in China between 1982 and 2020 using a modified anomalous accumulation method at the pixel level. We observed divergent patterns of “wet areas becoming drier, and dry areas becoming wetter” with rainfall amount and rainy days increasing in dry regions, and decreasing in humid regions. Wet seasons extend to dry areas and shorten in wet areas, with trends related to dryness. Simultaneously, as the dryness increased, the length, number of dry spells, and consecutive dry days increased. Concurrent increases in rainy days and dry spells indicated a seasonal rainfall regime toward greater variations in drier areas, which was not entirely consistent with a global intensification pattern of “dry getting drier and wet getting wetter”, implying increased potential climatic risks in dry areas. For climate risk prediction, water resource allocation, and agricultural management, we advocate a finer and more precise dynamic assessment of the wetting–drying pattern.