Research and analysis

South-east England water situation report: June 2026 summary

Updated 14 July 2026

Applies to England

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

June was a wet month with an average of 136% of the long term average (LTA) rainfall recorded across the south-east of England as unsettled conditions emerged from the high pressure experienced in May. Thames area (THM) was the driest area and Kent, South London and East Sussex area (KSLES) was the wettest. The first 11 days of the month accounted for an average of 82% of the monthly total rainfall. A heatwave developed from 20 June with unprecedented temperatures, resulting in red heat alerts being issued by the Meteorological Office for 3 days from 24 June. There were extensive overnight convective thunderstorms on 22 June in an arc from central THM, to southern Hertfordshire and North London area (HNL) to northern KSLES. These storms resulted in daily rainfall totals in excess of 30mm in these areas.

As would be expected at this time of year, the soil moisture deficits (SMDs) rose to end the month above the LTA and there was little recharge. One fluvial flood alert was issued during the month. Groundwater levels have continued to fall across the south-east of England, with 11 of the 16 indicator sites in the normal range for June.

1. Rainfall

June was a wet month with an average of 136% of the LTA rainfall recorded across the south-east of England. THM was the driest area, relatively, with 131% of the LTA for June and KSLES was the wettest with 143% of the LTA rainfall. The rainfall in early June halted the run of 3 consecutive months with below average rainfall.

The first 11 days of the month accounted for an average of 82% of the monthly total rainfall as unsettled conditions emerged from the high pressure experienced in May. A quarter of the monthly rainfall total was attributed to 1 June, when the highest daily rainfall total (54.1mm) was recorded at Worlds End, Solent and South Downs area (SSD). On 2 June at Cowfold, also in SSD, there was an intense summer storm which resulted in 18mm being recorded in 15 minutes.

A heatwave developed across England from 20 June with unprecedented temperatures, breaking the 1976 England temperature record on 24 June, then again on 25 and 26 of the month. In the south-east, this resulted in red heat alerts being issued by the Meteorological Office for this period, followed by amber heat alerts up to 28 June. There were extensive overnight convective thunderstorms on 22 June in an arc from central THM, to southern HNL to northern KSLES. These storms resulted in daily rainfall totals in excess of 30mm in these areas. On average, the rainfall on 22 June accounted for 11% of the monthly total rainfall, with the highest total of 35.6mm recorded at Beckenham College, KSLES. Around 33mm of this fell between 03:15 and 03:45, indicating the intensity of the thunderstorms. Little rainfall was recorded in the month after this date.

2. Soil moisture deficit and recharge

The SMDs fell slightly in response to the rainfall at the beginning of the month, then rose steadily to end the month above the LTA. As would be expected during the growing season, there was limited recharge during June which was close to the LTA for the month.

3. River flows

The seasonal decline in flows continued during June. The high SMDs and restricted spatial distribution of the rainfall resulted in muted responses to the heavy rainfall at the beginning of the month. For example, a raingauge near the River Loddon at Sheepbridge (THM) recorded 52mm in the first 10 days of June, yet there was hardly any response in the flows. A similar picture was evident for the Lymington River at Brockenhurst where 64mm rainfall was recorded in the same period but again, there was very little response at the gauging station. There was also little or no response by groundwater fed rivers, although localised heavy rainfall may have resulted in flows rising at both the River Mimram at Panshanger and River Ver at Colney Street (both HNL).

Flows at 14 of the 21 indicator sites were in the normal range for June. Three sites were in the above normal range, including the River Mimram at Panshanger (HNL) and the River Wey at Tilford (THM). Three sites were in the below normal range, including the River Kennet at Marlborough (THM). The River Coln at Bibury recorded notably low flows during June. One fluvial flood alert was issued during the month.

4. Groundwater levels   

Groundwater levels have continued to fall across the south-east of England, as would be expected for this time of year. Jackaments levels (Cotswolds, THM) were in the notably low range, matching the neighbouring indicator flow site at the River Coln at Bibury. Below normal groundwater levels were recorded at 4 of the 16 indicator sites, scattered across the Berkshire Downs (THM), North Downs (KSLES), South Downs and the Isle of Wight (SSD). Levels at the remaining 11 indictor sites were in the normal range for June, reflecting the legacy high levels from the wet winter experienced.

5. Reservoir stocks

Reservoir stocks fell during June at all reservoirs with just the exception of Farmoor (THM) which remained steady throughout the month and above the LTA for June. In addition to Farmoor, stocks at Bough Beech, Weir Wood, (both KSLES) and Lower Lee (HNL) were all above average. At Lower Thames (THM), Ardingly, Arlington (both SSD), Darwell and Powdermill (both KSL) reservoirs, stocks were below average for June. Bewl stocks (KSLES) remained close to the LTA.

Author: HNL Groundwater and Hydrology, 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.