Harrow, Pinner South
HA5 1AB in Harrow has a Medium flood risk - EA NaFRA2 data records 4 properties in a flood risk zone. Heat risk is Higher, with a median (50th percentile) of 38 days above 25°C per year, averaged over the 2021-2040 period under the RCP8.5 high emissions scenario (Met Office UKCP18). Air quality is High at PM2.5 8.3 μg/m³, above the WHO annual guideline of 5 μg/m³ (Defra UK-AIR). Ground conditions are High risk, with Prequaternary Marine/Estuarine Sand And Silt geology; shrink-swell risk is classed as probable (BGS GeoSure).
National comparison
Flood risk at HA5 1AB is rated Medium, based on Environment Agency NaFRA2 modelling.
Heat risk at HA5 1AB is rated Higher, reflecting Met Office UKCP18 climate projections (50th percentile) for this area, averaged over the 2021-2040 period under the RCP8.5 high emissions scenario. These are probabilistic projections - the 50th percentile is the central estimate within RCP8.5; the full range of modelled outcomes is wide and lower emissions scenarios would produce lower figures. Higher summer temperatures increase cooling energy costs, affect comfort in poorly insulated or south-facing properties, and can accelerate shrinkage in clay soils beneath foundations. Properties built before 1980 without cavity wall insulation are typically most affected.
Air quality at HA5 1AB is rated High, based on Defra UK-AIR annual mean PM2.5 data. Fine particulate matter (PM2.5) comes primarily from road traffic, industry, and domestic burning. Long-term exposure above the WHO guideline of 5 µg/m³ is linked to respiratory and cardiovascular health risks. Buyers and renters in higher air quality risk areas may wish to consider whether the property is near busy roads or industrial sources.
BGS GeoSure data classes the underlying soil at HA5 1AB as Prequaternary Marine/Estuarine Sand And Silt, with shrink-swell hazard rated probable (subsidence risk band: High). Soil type and shrink-swell behaviour drive subsidence claims following dry summers; recent ABI data shows insurer payouts rose sharply after the 2022 and 2025 hot summers. A structural survey is the reliable way to assess ground risk for a specific property.
This LocalRisk report for HA5 1AB draws on four official UK open data sources: Environment Agency NaFRA2 flood modelling, Met Office UKCP18 climate projections, Defra UK-AIR PM2.5 monitoring, and British Geological Survey GeoSure subsidence mapping. Risk ratings are a screening tool, complementing - not replacing - the searches and surveys ordered as part of a property transaction. Data covers Harrow and is updated as new official datasets are published.
Harrow has a suburban north-west London setting with higher ground and dense development and experiences cool, wet winters and warm summers, influenced by elevation and urban form.
Environment Agency flood zone data places HA5 1AB in the medium flood risk band. EA NaFRA2 data shows 1 at medium risk, 3 at low risk in this postcode. The band reflects the highest flood risk within the postcode; some properties within this postcode may face little or no direct flood risk. Individual properties within HA5 1AB can differ - a formal flood risk search is recommended before any property transaction.
Practical check: EA data flags 4 properties at flood risk here - check whether the property is among them by comparing its position to the flood zone boundary. 38 hot days are projected (UKCP18 50th percentile, 2021-2040 average under RCP8.5) - check which rooms face south or west and whether the property has cross-ventilation or external shading. With PM2.5 above WHO guidelines here, check which bedrooms face busy roads and how fresh air is drawn into living spaces. With prequaternary marine/estuarine sand and silt geology here, look for signs of ground movement - diagonal cracks above windows, sticking doors, and gaps between walls and extensions. These are postcode-level indicators - conditions vary between individual properties.