Event duration matters: spatial–temporal patterns of United States daily and multi-day precipitation extremes

Understanding the dynamics of extreme precipitation is essential for assessing flood risk, designing resilient infrastructure, and adapting to climate variability. This study examines the spatial and temporal characteristics of single-day and multi-day precipitation extremes across the contiguous United States using station-based observations from 1979 to 2023. The analysis is based on three categories: (i) daily (single 1-day) maxima, (ii) 3-day and 5-day accumulations, and (iii) event-based wet-spell accumulation. Using these indicators, we assess variability, event structure, and seasonality across the nine National Centers for Environmental Information (NCEI) climate regions. We first compare how precipitation indicators vary across durations and regions, including the contribution of the wettest day to multi-day events and the temporal co-occurrence of maximum 1-day and multi-day peaks. We then examine seasonal timing and trend patterns. Finally, we explore how duration-dependent extremes align with documented regional storm regimes. The results reveal distinct spatial and temporal contrasts between indicators, as well as among climate regions, characterizing how each indicator captures different, though partly overlapping, aspects of United States (U.S.) precipitation extremes. These spatial and seasonal differences are broadly consistent with regional storm regimes and precipitation characteristics documented in prior studies. By jointly analyzing 1-day and multi-day extremes using a unified set of indicators, this study provides a regionally nuanced perspective on the multidimensional nature of extreme precipitation and highlights the importance of precipitation persistence alongside peak intensity for flood-risk characterization and adaptation planning.