September was a dry and cool month; it was the coldest September since 1993 in the Central England Temperature series, and despite some unsettled spells there were periods of fine sunny weather. The UK registered just over half of the long-term average rainfall for September. All regions of the UK were drier than average, many substantially so, with the exception of Southern England. Scotland was particularly dry; in a series from 1910 only five Septembers have been drier. Most catchments in northern Britain registered normal to below normal flows, with notably low flows for the time of year in much of western Scotland and northern England. Further south, flows in many catchments remained above normal.
Below average rainfall meant that soil moisture deficits generally did not decline substantially in September. This allowed the continuation of seasonal recessions in most boreholes and groundwater levels generally remained in the normal range or just below. Stocks fell in the majority of index reservoirs but generally were above average for the time of year, notably so in some impoundments in the west of the UK. The onset of groundwater recharge will be sensitive to late autumn rainfall, but overall reservoir stocks for England and Wales remain above average and as such the water resources situation remains healthy entering the late autumn, a time when aquifer recharge typically commences.
Further details can be found here.