A rare “once-in-a-millennium” super rainstorm battered Zhengzhou, central China, during July 17^th to 22^nd 2021 (named “7.20” Zhengzhou super rainstorm), it killed 398 people and caused billions of dollars in damage. However, a pressing question is whether this level of intensity rainstorm could be quantitatively recorded by geologic archives, so that we can better understand its historical variability beyond the range of meteorological data. Here, three land snail shells (Cathaica fasciola) were collected from Zhengzhou in 2021 and weekly to daily resolved snail shell δ¹⁸O records from June to September of 2021 were obtained by IRMS and SIMS. The daily resolved records show a dramatic negative shift between June 18^th and September 18^th and we infer that this shift results from the “7.20” Zhengzhou super rainstorm according to the established age framework. Furthermore, the theoretical precipitation amount of “7.20” Zhengzhou super rainstorm calculated by the amplitude of this δ¹⁸O shift using flux balance model closely approaches to the precipitation amount observed at the local meteorological station. Our results suggested that the ultra-high resolution δ¹⁸O of land snail shells have the potential to quantitatively reconstruct local synoptic scale super rainstorm events and fossil snail shells in the sedimentary strata have the possibility to be valuable material for investigating the historical variability of local super rainstorms under different climate background conditions.

land snail,rainstorm,δ18O,paleoweather