Although previous studies of extreme precipitation have focused mainly on extreme daily rainfall, brief but heavy rain can cause flash flooding, severe damage and dangerous conditions. These sub-daily extremes are often confined to small areas that can be missed by rain gauge networks or satellites, and they are very far from being resolved by climate models. In this study, we find a robust positive trend of at least 20% per decade in sub-hourly extreme rainfall near Sydney, Australia, over 20 years, despite no evidence of trends at hourly or daily scales. This trend is seen consistently in storms tracked using multiple independent ground radars, is consistent with rain-gauge data and does not appear to be associated with known natural variations. This finding suggests that sub-hourly rainfall extremes may be increasing substantially faster than those on more widely reported time scales.

Ayat, H., Evans, J.P., Sherwood, S.C., Soderholm, J., 2022. Intensification of sub-hourly heavy rainfall. Science 378, 655–659.