In addition to predicted changes in climate, more frequent and intense severe weather events (e.g. tropical cyclones, severe storms and droughts) have been identified as serious and emerging threats to the World's freshwater crayfish. This paper documents a single, high intensity rainfall event (in an area known for phenomenal rainfall events) that led to a flash flood and mass mortality of Euastacus valentulus in the Numinbah Valley of southeast Queensland in 2008. Several hundred crayfish died after evidently being swept away and entrapped in vegetation or buried in alluvium during this single extremely high flow event. In light of our observations, it is clear that severe weather events have the capacity to substantially impact/deplete freshwater crayfish populations. This emerging climate-driven threat is seen as particularly significant for freshwater crayfish species that occupy single localities with highly restricted ranges. Clarification of geographic ranges would allow a priority list of the most "at risk" populations, which could prove useful in a management response to severe weather events, which are predicted to be more frequent in future.