Recent Spatiotemporal Trends in Extreme Rainfall Events in South Korea: From Sub‐Hourly to Multi‐Day Scales

ABSTRACT Understanding the spatiotemporal evolution of extreme rainfall is crucial for hydrologic design, infrastructure planning and disaster risk management, particularly in the context of a changing climate. In South Korea, intensifying rainfall extremes have been observed in recent decades; however, most existing studies have focused on hourly or daily timescales, offering limited insights into sub‐hourly and multi‐day variability. This study examined temporal trends in annual maximum precipitation (AMP) using data from 425 weather stations across South Korea from 2004 to 2024. Eight rainfall durations, ranging from 30 to 4320 min (3 days), were analysed. To identify monotonic trends, four statistical methods were employed: the Mann–Kendall test, the modified Mann–Kendall test, the block bootstrap Mann–Kendall test and linear slope estimation. The results reveal a pronounced dependence of AMP trends on rainfall duration. Short‐duration events (30–120 min) exhibited spatially scattered and mixed trends, likely driven by local convection. Long‐duration events (720–4320 min) showed distinct spatial patterns, with increases observed along the southern and southeastern coasts and decreases noted in central and northern inland regions. The spatial dispersion of AMP, measured by the coefficient of variation, has increased across all durations, indicating growing spatial heterogeneity in extreme rainfall. Collectively, these findings show that extreme rainfall in South Korea is becoming both more spatially uneven and increasingly duration‐dependent. These insights highlight the need to incorporate multi‐duration, spatially explicit information into hydrologic design standards and broader climate‐resilient planning efforts.