Research and analysis

South-east England water situation report: July 2025 summary

Updated 12 August 2025

Applies to England

• Publication for Northern Ireland
• Publication for Scotland
• Publication for Wales

1. Summary

July was the first month since March when above the long term average (LTA) rainfall fell, with 118% recorded across the south-east of England. The month was characterised by typically heavy isolated summer showers, with the top 3 daily rainfall totals occurring on different days through the month. The widespread heavy rainfall recorded across the south-east on 6 July accounted for a fifth of the monthly total. There were on average 17 ‘dry’ days where less than 0.2mm rainfall was recorded. The soil moisture deficits (SMDs) rose steadily during the month to end July on average 160% of the LTA across the south-east of England. Cotswolds West (Thames, THM) and Test Chalk (Solent and South Downs, SSD) both had the highest SMD on record for the end of July. There was limited effective rainfall during the month as would be expected with the high SMDs. There were 24 flood alerts and 2 flood warnings issued in July in response to the intense summer showers. Groundwater levels continued to fall during the month with 14 of the 16 indicator sites in the normal or below range for July. Hosepipe bans have been issued in parts of the south-east of England supplied by Thames Water and South East Water to preserve stocks and manage demand.

2. Rainfall

July was the first month since March when above the LTA rainfall fell, with 118% recorded across the south-east of England. Kent and South London (KSL) was much wetter than the other 3 areas of the south-east with 174% the LTA for July. By contrast, THM was drier with 84% of the LTA for the month.

The month was characterised by typically heavy isolated summer showers, with the top 3 daily rainfall totals occurring on different days through the month. The highest daily total (56.3mm) was recorded at Eastry, in the Stour catchment (KSL) on 6 July. Nearly 43mm of this fell in an hour. The second highest daily rainfall total (53mm) was recorded at Warnford, East Hampshire Chalk, SSD on 31 July. Once again a high proportion of the daily total fell in a limited time with 32mm falling in two and a half hours. The third highest daily total (42.8mm) was recorded on 20 July at Paddock Wood, Medway (KSL), nearly 28mm of which fell in an hour. The wettest day for Hertfordshire and North London (HNL) was 19 July, with totals close to 28mm being recorded at Wheathampstead, Lee Chalk.

The widespread heavy rainfall recorded across the south-east on 6 July accounted for a fifth of the monthly total. There were on average 17 ‘dry’ days where less than 0.2mm rainfall was recorded.

The 4 months ending July were the driest

• since 1976 for Cotswolds West (THM)
• since 1995 for Cotswolds East (THM)
• since 2010 for Cherwell (THM)
• since 2022 for the south-east of England, THM, HNL, SSD and KSL

3. Soil moisture deficit and recharge

The soil moisture deficits (SMDs) rose steadily during the month, with slight reductions in response to the rainfall on 6, 20 and 31 July to end on average 160% of the LTA across the south-east of England. The highest SMDs this month were in HNL, although were only the fourth highest on record after July 2022. The high SMDs in THM reflected the below average rainfall where Cotswolds West had the highest SMD on record for the end of July and Cotswolds East had the second highest SMD after 1976. Test Chalk (SSD) also had the highest SMD on record. As would be expected at this time of year, there was limited recharge across the south-east of England.

4. River flows

The seasonal decline of groundwater fed rivers continued during the month. However, the Ver at Colney Street and Mimram at Panshanger (both HNL) responded strongly to the localised rainfall on 19 July. The Stour at Horton (KSL) also responded to the rainfall on 19 and 20 July. Elsewhere, response to any rainfall was muted as a result of the high SMDs and the scattered distribution of the rainfall. Over half of the key indicator sites were in the normal or above band during the month. These were largely draining Chalk catchments. The Thames at Kingston and Farmoor (both THM) and the Lymington River (SSD) all had flows in the notably low category. The Coln at Bibury had the third lowest monthly flow on record, after 2022, and was in the exceptionally low range. There were 24 fluvial alerts and 2 fluvial warnings issued in response to the intense summer showers on 6, 7, 18, 19, 20 and 31 July.

5. Groundwater levels   

The expected steady decline of groundwater levels for this time of year continued during the month, with 14 of the 16 indicator sites in the normal or below range for July. Jackaments (THM) recorded levels in the exceptionally low category and had the lowest level recorded for July. Carisbrooke, IOW (SSD) registered the lowest levels since 1979. Both Lilley Bottom (HNL) and Stonor (THM) retained levels in the above normal category as a legacy of the wet winter.

6. Reservoir stocks

The high temperatures and lack of rainfall over the last few months has resulted in significant declines in reservoir storage. Lower Lee (HNL) and Weir Wood (KSL) reservoirs remained above the LTA. Bough Beech (KSL) storage was close to the LTA for July. Lower Thames (THM), Arlington (SSD), Bewl (KSL), Darwell (KSL) and Powdermill (KSL) were all below the LTA. Both Farmoor (THM) and Ardingly (SSD) ended the month close to the July minimum storage on record. Hosepipe bans have been issued in parts of the south-east of England supplied by Thames Water and South East Water to preserve stocks and manage demand..

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.