Informing Future Risks of Record‐Level Rainfall in the United States

The changing risk of extreme precipitation is difficult to project. Events are rare by definition, and return periods of heavy precipitation events are often calculated assuming a stationary climate. Furthermore, ensembles of climate model projections are not large enough to fully categorize the tails of the distribution. To address this, we cluster the contiguous United States into self‐similar hydroclimates to estimate changes in the expected frequency of extremely rare events under scenarios of global mean temperature change. We find that, although there is some regional variation, record events are projected in general to become more intense, with 500‐year events intensifying by 10–50% under 2 °C of warming and by 40–100% under 4 °C of warming. This analysis could provide information to inform regional prioritization of resources to improve the resilience of U.S. infrastructure. Key Points Spatial clustering can be used to create stable projections of extreme precipitation events Analysis over the United States suggests 1,000‐year events will be up to 5 times more frequent under 2 degree C warming Differences in projections between regions are evident, with the U.S. East Coast and mountain regions showing large intensification