POSTCODE AREA CLIMATE RISK
SY21 is a UK postcode district covering part of Llanfyllin, Powys. LocalRisk has flood, heat, air and ground-stability data for 872 postcodes in SY21.
2.1% of postcodes in SY21 fall into Natural Resources Wales's high flood-risk band - below the UK average of about 7%. The band reflects the highest flood risk within each postcode; some properties may face little or no direct flood risk. Two postcodes a few streets apart can land in different bands; what drives the gap is elevation, distance to the nearest watercourse, and how the surrounding drainage performs in heavy rain. The postcode list below links to the full address-level reading for each postcode in SY21.
Met Office UKCP18 projections (50th percentile) estimate around 12 days above 25°C per year for the area covering SY21, averaged over the 2021-2040 period under the RCP8.5 high emissions scenario. These are probabilistic projections - the full range of modelled outcomes is wide and lower emissions scenarios would produce lower figures.
Annual mean PM2.5 for the council area covering SY21 is 4.5 µg/m³ - close to the World Health Organisation guideline of 5 µg/m³. Postcodes within 200 metres of an A-road or major junction routinely run higher during weekday rush hours than residential streets two roads back.
Ground stability in SY21 follows the underlying geology more than the postal boundary. The British Geological Survey GeoSure dataset maps clay shrink-swell risk on a 50-metre cell, and properties on the same street can sit in different bands where a clay seam ends mid-road. A postcode-level check picks up that variation.
Flood risk - postcodes in SY21
NRW flood risk maps data. Postcode-level. Search below for your exact risk.