Thunderstorms forecast for parts of the UK this week carry a flash flooding risk that the record dry summer has made worse, according to the BBC.
The Met Office has warned that heavy showers falling on parched ground risk producing surface run-off and localised flooding rather than being absorbed. The BBC reports that some showers through Thursday will be very heavy and slow-moving. Hail, lightning, and localised flooding are possible, particularly across north-west England, Northern Ireland, and southern Scotland.
England recorded its driest July since records began in 1836, the Met Office confirmed, with just 10% of average monthly rainfall that month. Drought officials have declared 71.3% of England now in drought, according to the BBC.
During dry periods, ground becomes hard and compacted, increasing water repellence and surface run-off. When intense storm rainfall falls faster than baked soil can absorb it, the water travels over the surface rather than into the ground.
Surface water flash flooding is a distinct peril from river or coastal flooding, and standard flood risk maps often underestimate it. The Environment Agency (EA) now estimates around 4.6 million properties in England are at risk from surface water flooding. That is 43% higher than its previous estimate, based on data from the National Flood Risk Assessment published in December 2024. Most of those properties sit outside the river and coastal flood zones organisations have historically used to gauge exposure.
A property with no history of river flooding can still be vulnerable to surface run-off produced by slow-moving summer storms. That gap between perceived risk and actual exposure is worth keeping in mind when reviewing client cover this week. Previsico's 2025 State of Flood Resilience report found that 85% of businesses surveyed were concerned about surface water flooding, yet 65% lacked early warning systems. The report was based on responses from more than 100 senior leaders.
The Building Cost Information Service (BCIS) warned in August that the current drought could expose underinsurance in property cover. Cos Kamasho, principal consultant at BCIS, said rising reinstatement costs, gaps at renewal, and more frequent climate claims are converging. Policyholders risk finding their sums insured fall short only when a claim is made, he warned.
The average claim for damage to homes and possessions from flooding, storms and burst pipes rose to £8,548 in the second quarter of 2026. That represents a 12% increase year on year, per Association of British Insurers (ABI) data.
The BBC notes that heavy summer thunderstorms do not end a drought, as rivers, groundwater, and reservoirs can remain depleted for months.
The EA has described the rapid swing from drought to flooding as "weather whiplash". Climate change, it has said, is producing longer, hotter summers and more intense rainfall. Drought and flood are increasingly forming part of the same weather sequence rather than alternating.
For brokers reviewing property cover, two checks are worth making before a loss occurs rather than after. Standard flood cover typically includes surface water flooding, but policy wording varies. Some commercial policies impose higher excesses or limit cover to specific named perils.
Flood Re, the government-backed reinsurance scheme supporting affordable flood cover for eligible residential properties, does not cover commercial properties or homes built after 2009. Brokers placing cover for clients outside Flood Re eligibility should confirm that surface water flooding is adequately addressed in the programme. The EA's flood risk checker does not always flag surface water exposure, so broker-level assessment matters here.
