BRISTOL CLIMATE INSIGHTS
2 March 2026 - LocalRisk
Analysis of Environment Agency flood zone data reveals 3,501 of Bristol's 11,746 postcodes fall within high flood risk areas — placing the city 4th nationally among councils with 5,000 or more postcodes.
Bristol has one of the UK's highest flood exposures - 29.8% of postcodes are in high flood-risk zones, 4th nationally. Analysis of 61,223 properties and per-year weather data from LocalRisk.
Nearly one in three properties falls within an Environment Agency high flood risk zone - 18,532 of 61,223 assessed properties. The River Avon runs directly through the city centre, and tidal influence from the Severn Estuary extends flood exposure further inland than in most other UK cities. Flood risk reaches the urban core.
Analysis of Environment Agency flood zone data across all 11,746 Bristol postcodes shows 3,501 postcodes fall within high flood risk areas. A further 1,548 sit in medium risk zones. Taken together, over 43% of Bristol's postcodes carry elevated flood risk (combining high and medium risk zones; 29.8% fall within high risk only) - placing the city 4th nationally among councils with 5,000 or more postcodes, behind only Sefton (71%), West Suffolk (37%), and East Lindsey (34%).
The city centre and harbourside are the most exposed. BS1 2AL tops the list with 90 properties - every single one classified as high flood risk. The pattern continues through the BS1 postcode area: BS1 6JU (88 properties, 100% high risk), BS1 2AR (88), BS1 6WH (84), BS1 2AS (79), BS1 3EQ (76).
These are not empty plots - they include homes, offices, and shops in some of Bristol's most visited streets.
Beyond the centre, the BS4 (Brislington/Knowle), BS9 (Westbury-on-Trym), BS10 (Henbury/Brentry), and BS7 (Bishopston/Horfield) areas all contain postcodes where every assessed property faces high flood risk.
> In total, Bristol has 61,223 assessed properties. Of those, 18,532 (30.3%) are high risk, 12,885 (21.0%) are medium risk, and 29,806 (48.7%) are low risk.
Among England's major cities with 5,000 or more postcodes, Bristol's high flood risk rate of 29.8% is significantly above the next large urban authority - Leicester at 20.9%. London boroughs like Brent (26.9%) and Hillingdon (26.7%) also feature, but Bristol is the largest single council area in the top five.
| Council | High Flood Risk % | Total Postcodes | |---|---|---| | Sefton | 71.1% | 6,705 | | West Suffolk | 36.8% | 5,362 | | East Lindsey | 33.6% | 5,277 | | Bristol | 29.8% | 11,746 | | Brent | 26.9% | 5,915 |
_Source: Environment Agency flood zone data, analysed by LocalRisk._
The 43% figure above counts all postcodes with any elevated flood risk - both high and medium zones. The table uses high risk only, so the numbers are comparable across councils.
The risk classifications above are based on Environment Agency flood zone modelling. But what does longer-term climate data show for Bristol?
Bristol's annual rainfall is around 782mm (Met Office Filton station, 1991-2020) - less than Manchester (~850mm) but above Cambridge (548mm) and Newcastle (~650mm, Met Office Durham station). Brighton's comparable figure is approximately 800mm (Herstmonceux station). Leeds city centre is estimated at around 660mm based on surrounding station data. Recent years have been considerably wetter: Bristol recorded 1,199mm in 2023 and 1,224mm in 2024, both well above average, before returning to 947mm in 2025. The 2023-2024 period was exceptionally wet across the UK, and Bristol's figures for those years should be read in that context.
Across 2023-2025, Bristol averaged 36 wet days per year - days recording 10mm or more of rainfall - and 164 rain days per year overall. 2024 brought 104 km/h wind gusts - storm-force conditions that compound flood risk by overwhelming drainage systems. 2025 was drier overall but hotter, with Bristol reaching 32.5°C and 18 days above 25°C.
| Year | Rainfall | Wet Days (≥10mm) | Hottest Day | Frost Days | |---|---|---|---|---| | 2023 | 1,199mm | 43 | 28.4°C | 30 | | 2024 | 1,224mm | 40 | 27.7°C | 12 | | 2025 | 947mm | 24 | 32.5°C | 21 |
_Source: Open-Meteo Historical Weather Archive (ERA5 reanalysis), 2023-2025. Note: 2023 and 2024 were among the wettest years on UK record and are above Bristol's long-term average of ~782mm (Met Office Filton station, 1991-2020)._
On heat, Bristol's 30-year ERA5 average is around 5.5 days above 25°C per year (ERA5 analysis, 1991-2020). The 2023-2025 period averaged 12.7 hot days - above the ERA5 1991-2020 baseline due to unusually warm summers.
Met Office UKCP18 climate projections put Bristol at around 24 days above 25°C as a central estimate for the 2030s (2021-2040 period). That is more than four times the ERA5 1991-2020 baseline of 5.5 days, and substantially above the 12.7 days observed on average across 2023-2025.
These are probabilistic projections derived from the Met Office UKCP18 ensemble under a high emissions scenario (RCP8.5, 50th percentile) - the same data that powers the risk scores on LocalRisk postcode pages. The full range of modelled outcomes is wide. Under lower emissions scenarios the central estimate would be materially less; under the high end of the ensemble it would be higher. The direction of travel - more hot days, more intense heat events, and increasing compound risk from heat and heavy rainfall - is consistent across the range.
For a city where nearly a third of properties already sit in high flood risk zones, more intense rainfall events alongside rising temperatures create compounding risk - wetter winters that can overwhelm drainage systems, and hotter summers that increase the strain on older urban infrastructure.
_Source: Met Office UKCP18 climate projections (2021-2040 period, RCP8.5, 50th percentile). Observed baseline: Open-Meteo ERA5 reanalysis, 1991-2020._
Bristol's air quality picture is more moderate. The city's average PM2.5 reading of 6.6 µg/m³ falls within the Medium band nationally - above the 5 µg/m³ WHO guideline, but well below the levels recorded in parts of inner London or the industrial Midlands. The primary contributors are road traffic and the dispersal effects of Bristol's valley topography.
On heat, Bristol's ERA5 1991-2020 average of around 5.5 days above 25°C per year reflects its position in the South West - warmer than northern cities but not yet approaching the extreme heat exposure of parts of London or the Thames Valley. The projections suggest this will change significantly within the next two decades.
Unlike many South East and Midlands councils, Bristol has a notably low subsidence risk. Zero percent of postcodes are classified as probable shrink-swell clay risk, reflecting the city's predominantly sandstone and limestone geology. Subsidence insurance claims and mortgage complications are far less common in Bristol than in clay-heavy areas like parts of Essex, Kent, or the East Midlands.
Bristol's green space access figure of 18.6% means roughly one in five hectares within 200 metres of the average postcode is classified as green space - above the national urban average and ahead of Manchester (14.7%), Leeds (15.9%), Brighton (15.6%) and Cambridge (17.9%).
The city's valley topography and network of urban parks - including Clifton Down, Ashton Court, and the Frome Valley greenway - contribute to a relatively accessible green environment despite Bristol's density. Postcodes in the Clifton, Redland and Cotham areas have particularly high green space access, while industrial riverside areas and parts of south Bristol score lower.
_Source: LocalRisk green space analysis using Ordnance Survey data._
EA flood zone classification means an area carries a meaningful probability of flooding from rivers, sea or surface water - not that any specific property will flood. For homeowners and buyers, that means higher insurance premiums, potential difficulty selling, and the practical risk of water damage.
High-risk areas are concentrated along the Avon valley floor and lower-lying suburbs: BS1 (city centre and harbourside), BS4 (Brislington), BS9 (Westbury-on-Trym), BS10 (Henbury), and BS7 (Bishopston) all contain postcodes where every assessed property carries high flood risk. Lower-risk areas are found at higher elevation: Clifton, Redland, and Cotham typically record substantially lower flood exposure, reflecting their position above the valley floor.
Bristol's position in the Avon valley, combined with tidal influence from the Severn Estuary, creates a particular vulnerability. The risk spreads across nearly a third of the city. Check any Bristol postcode directly at localrisk.co.uk for a full five-risk breakdown.
Bristol combines high flood exposure, above-average rainfall, and rising heat projections. Its subsidence and air quality profiles are more reassuring.
You can check the flood, heat, air quality, and subsidence risk for any UK postcode - free - at localrisk.co.uk. Bristol's full council breakdown, including a comparison of every postcode in the city, is at localrisk.co.uk/council/bristol-city-of.
Data sources: Environment Agency flood zone and surface water risk data; DEFRA UK-AIR PM2.5 monitoring; British Geological Survey shrink-swell clay risk assessment; Met Office 1991-2020 station normals (Filton station); Open-Meteo Historical Weather Archive (ERA5 reanalysis, ECMWF), long-term baseline 1991-2020; Met Office UKCP18 climate projections (2021-2040 period, RCP8.5, 50th percentile). Analysis by LocalRisk. _Methodology: Annual rainfall uses Met Office 1991-2020 station normals (Filton station, ~782mm). Hot-day counts use Open-Meteo ERA5 reanalysis (1991-2020 baseline). Recent observed weather (2023-2025) is ERA5 2023-2025. Climate projections use Met Office UKCP18 (the same source as LocalRisk postcode risk scores); RCP8.5 is a high emissions scenario and the 50th percentile represents the central estimate - outcomes under lower emissions would be less severe. Days above 25°C are used as the hot-day threshold for consistent cross-city comparison; the UK Heat Health Alert trigger is typically 28-30°C depending on region._
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