Climatology of Heavy Rain Events in the United States from Hourly Precipitation Observations

Flash flooding is frequently associated with heavy precipitation (defined here as ≥1 in. h−1) occurring over a short period of time. To begin a study of flash flood–producing rain events, the Hourly Precipitation Dataset (HPD) is used to develop a climatology of heavy rains on timescales of 3 h or less across the contiguous United States. Analyses of this dataset show a distinct seasonal cycle in the distribution of heavy rain events that begins along the Gulf Coast and expands into the midwestern states during the summer. This general evolution is very similar to that observed for flash floods, suggesting that the HPD can help in defining the climatological threat for flash floods.