A study has been undertaken of the most extreme short-period rainfall events in the UK of the 20th century. The events were classified using Bilham’s (1935) method of distinguishing rarity based on the depth-duration profile of the rainfall. Data was then collected for each of the events and the atmospheric conditions prior to each event were examined. This paper presents the results of this study, showing the commonalities and differences between the situations prior to the various events. It is believed that the findings can be used to identify situations in which extreme rainfall events may develop over the British Isles and therefore provide guidance to forecasters of the likelihood of extreme rainfall.

Many of the events led to flash-flooding and consequent loss of life and substantial property damage. The differences in surface conditions which determine whether a flood will result from accumulated rainfall are shown and provide a further tool for the assessment of flood risk.