Evidence of Emerging Increasing Trends in Observed Subdaily Heavy Precipitation Frequency in the United States

Abstract The magnitude and frequency of heavy precipitation are expected to increase under warming temperatures caused by climate change. These trends have emerged in observational records but with much larger evidence on a daily rather than a subdaily scale. Here, we quantify long‐term changes in heavy precipitation frequency in the United States using hourly observations in 1949–2020 from 332 gauges. We demonstrate that, when analyzed collectively, the frequencies of heavy precipitation at multiple durations from hourly to daily exhibit an increase that cannot be explained by natural climate variability. Upward trends are significant at ∼20%–40% of the gauges throughout the country except for the coastal western and southeastern regions, with higher percentages for longer durations. We also show that the frequency of hourly heavy precipitation has mainly grown after ∼2000, thus explaining the limited evidence of trends at the subdaily scale reported in past studies.