Research and analysis

Water situation: May 2024 summary

Updated 12 December 2024

Applies to England

May was another wet month across England, with most catchments receiving above average rainfall. England as a whole received 141% of the long term average (LTA) for the time of year. Soil moisture deficits (SMD) remain close to zero across northern and western parts of England, although soils have begun to dry in parts of the south-east, and south-west England. Monthly mean river flows decreased at most sites, but almost all sites were still classed as normal or higher in response to continuous, above average rainfall. Groundwater levels told a similar story, with almost all sites recording decreased levels at the end of May but almost all sites continue to be classed as normal or higher. Reservoir storage decreased at almost two-thirds of the reservoirs we report on, although changes were small. Storage for England is considered above average for the time of year with a volume of 95% of total capacity at the end of May.

1. Rainfall

The rainfall total for England for May was 83.9mm which represents 141% of the 1961 to 1990 LTA for the time of year (151% of the 1991 to 2020 LTA). The greatest rainfall totals were reported in the north-east and north-west of the country. Catchments in north-west England reported the greatest rainfall with Eden reporting 143mm which represents 193% of the LTA. In contrast West Cornwall in south-west England reported 52mm which is equal to 81% of the LTA.

Rainfall totals for May were classed as normal or higher in all catchments across England, with many catchments (80%) classed as above normal or higher for the time of year. Eight catchments in the north-east, north-west, east, and south-west of the country were classed as exceptionally high. Across the country just over a quarter of catchments (36) concentrated in north, east and south-west England were classed as notably high for the time of year. Almost half of England’s catchments (67) mainly in central and south-eastern areas of the country were classed as above normal. Additionally, a fifth of catchments mostly in the south-east, south-west and west of the country were classed as normal for the time of year. The 3-month cumulative rainfall totals were exceptionally high for almost two-thirds of catchments (81) across England. The previous 6 months and 12 months totals were even wetter, with both periods reporting nearly all catchments throughout the country (94%) classed as exceptionally high.

 At a regional scale, rainfall throughout most of the country was classed as above normal, with only north-west England classed as notably high. For England as whole rainfall was classed as notably high for the time of year.

2. Soil moisture deficit

Despite above average rainfall across England, the warmer temperatures and increased evapotranspiration associated with spring have helped soils in some parts of England begin to dry. Increases in SMD were observed in east, south-east, and south-west England compared to the previous month, while central and northern parts of the country continue to experience deficits of close to zero.

SMDs across England increased throughout the first three weeks of the month reaching deficits not observed since September 2023. However, during the final week of May SMD across England decreased leaving soils wetter than the LTA for the time of year. Overall soils across England, relative to the LTA, were even wetter at the end of the month than observed at the start.

3. River flows

Monthly mean flows decreased at almost all indicator sites (95%) during May. However, monthly mean river flows at all reporting sites continue to be classed as normal or higher for the time of year. The highest flows were observed in north-east, south-east, and south-west England. Eleven sites (35% of the total) were classed as exceptionally high, followed by 15 sites (27%) reporting as notably high for the time of year. Additionally, flows at 22 sites (40%) were classed as above normal, with a further 7 sites classed as normal.

Despite decreasing flows across most of the country, 4 sites recorded their highest monthly mean flows for May on record (record start given in brackets), in the:

• south-east, Allbrook & Highbridge, River Itchen (since 1958)
• south-east, Ardingley, River Ouse (since 1979)
• south-east, Kingston (Naturalised), River Thames (since 1951)
• south-west, East Stoke, River Frome (since 1965)

All regional indicator sites saw a decrease in monthly mean flows in May.

Haydon Bridge on the South Tyne, and Kingston Naturalised on the Thames, in the north-east and south-east respectively were classed as exceptionally high. In east England, the Bedford Ouse was classed as notably high, while The River Lune in the north-west, the River Dove in central England, and Great Stour in the south-east were classed as above normal. Only one site the River Exe in the south-west England was classed as normal for the time of year.

4. Groundwater levels   

At the end of May, groundwater levels had decreased at almost all the sites we report on (96%); only a single location Crossley Hill in north-east England reporting an increase in level. Despite many sites reporting decreases in groundwater levels during May, all reporting sites are classed as normal or higher for the time of year. Groundwater levels at 10 sites were classed as exceptionally high for the time of year, with a further 10 classed as notably high. In addition, 3 sites were classed as above normal, with a further 3 sites classed as normal for the time of year.

Six sites recorded their highest end of May level on record (record start given in brackets):

• Four Crosses (since 1990) in Staffordshire Sandstone in central England
• Weir Farm (since 1983) in Bridgnorth Sandstone in central England
• Coxmoor (since 1990) in Idle Torne Sandstone in central England
• Aycliffe (since 1979) in Skerne Magnesian Limestone in the north-east
• Priors Heyes (since 1972) in West Cheshire Sandstone in the north-west
• Skirwith (since 1978) in Carlisle Basin Sandstone in the north-west

Groundwater aquifer index sites across the country were reporting decreases in level by the end of May. Four sites were classed as exceptionally high for the time of year:

• Little Bucket (Stour Chalk)
• Skirwith (Carlisle Basin Sandstone)
• Stonor Park (South West Chilterns Chalk)
• Weir Farm (Bridgnorth Sandstone)

An additional 3 sites were classed as notably high:

• Chilgrove (Chichester Chalk)
• Dalton Estate Well (Hull and East Riding Chalk)
• Redlands Hall (Cam and Ely Ouse Chalk)

Jackaments Bottom (Burford Jurassic Limestone) was the only aquifer index site classed as normal for the time of year.

5. Reservoir storage

Reservoir storage decreased during May at almost two-thirds of the reservoirs and reservoir groups we report on, although these decreases were 6% or less. Of the 10 sites (32% of the total) which saw storage increase, Grafham reservoir in central England recorded the largest increase of 4%. Two reservoirs, Vyrnwy and Stithians were reporting as 100% full at the end of the month. By the end of May, almost all reservoirs or reservoir groups were classed as normal or higher for the time of year, with only the Dee System reporting as below normal due to ongoing maintenance work.

At a regional scale, total reservoir storage showed little change at the end of May, with the largest increase being 2% in south-east England. For England as a whole, storage remained at 95% of total capacity at the end of May.

6. Forward look

June began with relatively settled, drier conditions. Following this brief dry spell, mid-June is likely to be dominated by spells of sunshine and showers with an increased chance of heavy, thundery downpours. Towards the end of June drier, sunnier weather can be expected but the chances of showers and longer spells of rainfall remain. Temperatures throughout June are likely to be close to or above the climatological average for the time year.

For the 3 month period between June and August, there is a higher likelihood that the UK will experience warmer conditions for the time of year with an increased chance of heat waves and heat related impacts.

7. Projections for river flows at key sites

By the end of September 2024, river flows are projected to be normal or higher across England, with the greatest flows projected in east and south-east England, where many sites are projected to be normal or higher.

By the end of March 2025, river flows throughout England are projected to be normal although flows at couple of sites in south-east and east England have a greater likelihood of above normal flows

8. Projections for groundwater levels in key aquifers

By the end of September 2024, groundwater levels across England have a greater likelihood of being normal or higher, with sites in chalk and sandstone aquifers likely to be above normal or higher.

By the end of March 2025, groundwater levels across most of England have a greater likelihood of being normal or higher.

Author: National Water Resources Hydrology Team

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained in this report.