South-east England water situation report: May 2026 summary
Updated 11 June 2026
Applies to England
© Crown copyright 2026
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May was the third consecutive month when below average rainfall was recorded across south-east England when just 50% of the long term average (LTA) rainfall fell. The south-east recorded the driest two months for April and May since 2011.
The lack of rainfall and record breaking high temperatures during the last week of May caused soil moisture deficits (SMDs) to rise steadily during the month. The SMDs ended more than a third higher than the end of month LTA, and similar to the SMDs in May 2025. The combination of low rainfall and very high SMDs resulted in little or no recharge across the south-east.
River flows fell throughout the month and only a handful of sites showed any notable response to the heavy rainfall on 18 May. Flows ranged from exceptionally low at Brockenhurst (Solent and South Downs, SSD) to above normal at Panshanger (Hertfordshire and North London, HNL). No fluvial flood alerts were issued in May. Groundwater levels fell at all key indicator sites across the south-east and ended the month as normal for May at most sites. The last remaining groundwater food alert in Thames (THM) was removed during May.
1. Rainfall
May was the third consecutive month when below average rainfall was recorded across the south-east of England. Rainfall ranged from normal on the south coast and Isle of Wight to below normal across SSD and Kent and South London (KSL) to notably low for much of THM and HNL. The Roding areal unit in the far east of HNL had exceptionally low rainfall for May.
There was 50% of the LTA rainfall recorded across the south-east. Only 30% LTA was recorded in HNL which was the ‘driest’ area during May. Around a quarter of the monthly total fell on 18 May across the south-east and much of this rainfall fell along the south coast in SSD, yet SSD still only recorded 63% of the monthly LTA. The highest daily total was in SSD, on 18 May at Plumpton where 23.1mm was recorded. All of the top 5 highest totals for the month across the south-east were recorded in SSD.
The south-east recorded the driest two months for April and May since 2011, THM the third driest May since 1896 and HNL the driest two months ending in May on record.
2. Soil moisture deficit and recharge
The lack of rainfall and then the very hot temperatures during the last week of May caused SMDs to rise steadily during the month with a short and small dip in most areal units during the wet weather around 18 May. By the end of the month SMDs were more than a third higher than the end of May LTA and similar to the SMDs at the end of May 2025. The combination of low rainfall and very high SMDs resulted in little or no recharge across the south-east for the third month running.
3. River flows
River flows fell throughout the month and only a handful of sites showed any notable response to the heavy rainfall on 18 May. Flows ranged from exceptionally low at the Lymington River at Brockenhurst (SSD) to above normal at the Mimram at Panshanger (HNL). Lymington River had the fourth lowest monthly mean flows for May. Sites where flows were lower were generally draining impermeable catchments or where the local groundwater levels had fallen sharply, such as in the Cotswolds. The sites fed by groundwater in HNL, SSD and the Darent in KSL were normal for the time of year. Unsurprisingly, no fluvial flood alerts were issued in May.
4. Groundwater levels
Groundwater levels fell at all key indicator sites across the south-east and ended the month as normal for May at most sites. There were a few exceptions including West Meon Hut (SSD) and Little Bucket (KSL) which ended the month at above normal levels. Jackaments (THM) and Carisbrooke Castle (SSD) fell to notably low levels. Both these sites respond quickly to wet or dry weather and during May fell sharply to be lower than May last year. The last remaining groundwater flood alert in THM was removed during May.
5. Reservoir stocks
Reservoir stocks fell during May at all reservoirs with just the exception of Farmoor (THM) which remained steady throughout the month and above the LTA for May. In addition to Farmoor, stocks at Bough Beech, Weir Wood, Bewl (all KSL) and Lower Lee (HNL) were all above average. At Lower Thames (THM), Ardingly, Arlington (both SSD), Darwell and Powdermill (both KSL) reservoirs, were all below average for May.
Author: groundwaterhydrology@environment-agency.gov.uk
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.