May was a mixed month, with below average rainfall in the south and west of the UK, whilst substantially above average rainfall was registered in north-eastern Scotland; at the national scale, this resulted in a near average May total for the UK. River flows were generally below normal to notably low, with many catchments registering less than 60% of average; with below normal flows in accumulations extending back to at least the summer of 2017 in the south‑east of England. Soil moisture deficits (SMDs) increased and remained drier than average for Great Britain, particularly in southern England. Average outflows for England for May were the third lowest in a series from 1961. Groundwater levels commenced or continued their seasonal recession and the majority of levels were below normal at the end of May. Despite low rainfall in England and Wales, reservoir stocks remained near average. In Northern Command Zone, Bradford Supply and Derwent Valley groups and at Roadford, stocks were less than 80% of capacity and more than 10% below average; stocks in the south-east of England however, remained near average. On the basis of the hydrological situation at the end of May, further environmental and agricultural stress appears likely for the summer of 2019. However, an exceptionally wet start to June has ameliorated these pressures in some areas (with some localised flooding reported) but the impact of much longer-term rainfall deficits is still likely to be felt, especially in groundwater-dominated catchments.