Cambridge Flood Risk: The UK's Driest City Has Its Highest Inland Flood Risk

Cambridge's climate: one of England's driest major cities, with some of its highest risk

Cambridge receives around a third less rain than Manchester - yet has more than double Manchester's flood exposure, hotter summers than Bristol or Leeds, and nearly nine in ten postcodes on shrink-swell clay.

With a long-term average of around 548mm of rainfall a year (Met Office NIAB station, 1991-2020) - making it one of England's driest major cities - Cambridge is drier than Brighton, Oxford, Bristol, Leeds, and Manchester. Recent years have been wetter than normal: Open-Meteo ERA5 data for 2023-2025 recorded an average of 743mm, driven by unusually wet conditions in 2023 (790mm) and 2024 (851mm), before returning closer to the long-term average in 2025 (587mm).

On heat, Cambridge averages around 10.9 days above 25°C per year based on ERA5 climate data for 1991-2020 - the highest of any city in our analysis on the long-term baseline. Recent years have been warmer: the 2023-2025 period averaged 25.3 hot days, driven by exceptionally hot summers in 2023 and 2024. The contrasts stand out even on the long-term baseline: Cambridge is hotter in summer than any comparable English city, has higher flood risk than Oxford, Leeds, or Manchester despite receiving far less rain than any of them, and 35% of its postcodes sit on land assessed as probable shrink-swell clay subsidence risk.

Cambridge sits deeply inland at the edge of the Fens, with no sea breezes or hills to moderate its climate.

The heat: hotter than Bristol, hotter than Manchester

Cambridge averages around 10.9 days above 25°C per year based on ERA5 climate data for 1991-2020 - the highest of any city in our analysis on the long-term baseline. Oxford, the closest comparison, reaches around 8-10 days on a similar baseline. The gap is consistent with Cambridge's exposed inland position - no sea breeze, no significant topography, and flat surroundings that warm quickly under summer sun.

During major heat events, the city has fewer moderating influences than coastal areas. During the 2022 UK heatwave, Cambridge recorded temperatures among the highest measured in England, reflecting its exposed inland position and the absence of any coastal moderating effect.

| City | Days >25°C/yr (30-yr avg) | Annual rainfall (mm, Met Office) | Sunshine (hrs/yr, Met Office) | |---|---|---|---| | Cambridge | 10.9 | 548 (NIAB station) | 1,494 | | Bristol | 5.5 | 782 (Filton station) | 1,487 | | Manchester | 4.0 | ~850 (Woodford station) | ~1,385 | | Leeds | 4.7 | ~660 (city estimate) | ~1,350 | | Brighton | 3.6 | 799 (Herstmonceux station) | 1,687 | | Newcastle | 2.4 | 650 (Durham station) | 1,333 |

_Source: Hot days: Open-Meteo Historical Weather Archive (ERA5 reanalysis), 30-year average 1991-2020. ERA5 temperature uses ~28km grid cells; cities within ~60km may share grid cells, so hot-day figures should be read as regional rather than precise city-level values. Rainfall and sunshine: Met Office 1991-2020 station-based averages. Recent observations (2023-2025) were higher for all cities._

At the other end of the year, Cambridge has some of England's coldest winters for a southern city. It averages around 13 cold spells per year - defined here as three or more consecutive nights at or below 5°C (ERA5 analysis, 1991-2020) - comparable to Newcastle upon Tyne, compared to around 10 in Brighton. The same inland exposure that warms the city quickly in summer leaves it unprotected from cold easterlies in winter. Cambridge has a more continental climate than its latitude suggests.

The flood paradox: dry city, elevated river risk

Cambridge's flood picture confounds expectations. At 23.9% of postcodes intersecting Environment Agency high-risk flood zones - around 700 of the city's 2,960 postcodes - it sits above the flood exposure of Leeds (13.8%), Brighton (12.4%), and Manchester (10.2%), all of which receive considerably more rainfall.

The risk comes from the rivers, not direct rainfall.

Cambridge lies where the River Cam meets the wider Great Ouse drainage catchment, flowing through some of the lowest-lying land in England. Much of the eastern side of the city - the Riverside area, Chesterton, the Fen Road corridor, parts of CB1 around Coleridge - sits on low-lying floodplain and former fenland that drains slowly and can flood when river levels rise. Flooding often follows sustained rainfall across the wider Great Ouse catchment, rather than heavy rain directly over Cambridge itself.

| City | High flood risk % | Annual rainfall (mm, Met Office) | |---|---|---| | Bristol | 29.8% | 782 | | Cambridge | 23.9% | 548 | | Leeds | 13.8% | ~660 | | Brighton | 12.4% | 799 | | Manchester | 10.2% | ~850 | | Newcastle | 15.8% | 650 |

_Source: Environment Agency flood zone data, analysed by LocalRisk. Rainfall from Met Office 1991-2020 station-based averages._

As with all EA postcode-level data, the percentage reflects postcodes where any part of the area overlaps an Environment Agency high-risk flood zone. Flood risk in Cambridge is not evenly distributed - higher ground around the university colleges and the hills to the south carry much lower risk than the river corridors and lower-lying eastern suburbs.

Subsidence: Cambridge's least-discussed risk

The most notable figure in Cambridge's climate profile is its subsidence exposure. 35.3% of postcodes are assessed as probable shrink-swell clay risk by the British Geological Survey, with a further 53.6% assessed as possible. Taken together, nearly nine in ten Cambridge postcodes carry some assessed level of clay subsidence exposure.

For comparison:

| City | Probable subsidence % | Possible subsidence % | |---|---|---| | Cambridge | 35.3% | 53.6% | | Oxford | 11.2% | 37.6% | | Brighton | 0.0% | 0.0% | | Bristol | 0.0% | 0.0% | | Manchester | 0.0% | 0.0% |

_Source: British Geological Survey shrink-swell clay risk assessment, analysed by LocalRisk. Cities showing 0% reflect postcodes outside BGS-mapped shrink-swell zones in this dataset._

The cause is geology. While southern Cambridge extends onto the chalk of the East Anglian Heights, much of the city is underlain by Gault Clay - a reactive formation that shrinks in dry summers and expands again in wet winters. The same hot, dry summers that push Cambridge's heat figures above those of Bristol or Manchester also dry the clay beneath buildings. Cambridge's combination of hot summers and cold winters makes this movement cycle more pronounced than in wetter, milder cities.

Shrink-swell clay movement is one of the most common causes of ground movement insurance claims in English housing. In a city where average house prices sit well above the national average, subsidence exposure is a material consideration in any property assessment.

> 35% of Cambridge postcodes are assessed as probable shrink-swell clay risk - the highest of the cities analysed here. Brighton and Bristol both record 0%.

Air quality

Cambridge's PM2.5 reading of 7.4 µg/m³ places it above the WHO guideline of 5 µg/m³ and toward the higher end of our comparison cities - above Brighton (6.7), Bristol (6.6), and Newcastle (6.2), and comparable to Leeds (7.4).

The main contributors are road traffic on the A14 and A10 corridors, and the flat inland position that offers less natural wind dispersal than coastal cities. Brighton benefits from consistent sea breezes that dilute traffic pollutants; Cambridge has no equivalent mechanism.

Green space

Cambridge records 17.9% of land within 200m of postcode centroids classified as green space - above Manchester (14.7%), Brighton (15.6%) and Leeds (15.9%), and below Bristol (18.6%) and Newcastle (22.3%). The city benefits from a notable concentration of open land: the Backs (the open meadows behind the university colleges), Jesus Green, Midsummer Common, and Parker's Piece provide accessible green space within walking distance of much of the city centre. The Cam corridor itself adds to the accessible green land.

Cambridge's climate profile

Cambridge is drier than Brighton yet more flood-prone than Manchester. Further south than Manchester, it endures as many cold spells as Newcastle. Its summers rival those of cities far warmer on paper, while its geology creates a subsidence exposure that may not be apparent from a standard property check.

The same landscape that produces fewer rainy days than Brighton also produces hotter summers that dry the clay beneath buildings, and rivers that can flood even when Cambridge itself has barely seen rain.

Cambridge is a flat inland city built on clay at the edge of the Fens. It warms fast in summer and drains slowly when rivers rise.

Projected heat by 2040

Met Office UKCP18 climate projections put Cambridge at around 37 days above 25°C as a central estimate for the 2030s (2021-2040 period) - more than three times the ERA5 1991-2020 baseline of 10.9 days. These are probabilistic projections from the Met Office UKCP18 ensemble (high emissions scenario, RCP8.5, 50th percentile) - the same methodology that powers the heat risk scores on LocalRisk postcode pages. The full range of modelled outcomes is wide. The low end of the UKCP18 ensemble could produce substantially fewer hot days; the high end, substantially more. Outcomes would also be lower under lower emissions scenarios. What is consistent across the range is the direction: Cambridge is one of the cities in this analysis most exposed to projected increases in summer heat, combining high baseline hot-day counts with limited coastal or topographic moderating influence.

For buyers and movers

For buyers and movers, Cambridge's climate profile has two risks that are easy to underestimate.

Flood risk is concentrated in the river corridors, not distributed evenly. The Riverside area, Chesterton, the Fen Road corridor, and parts of CB1 around Coleridge sit on low-lying former fenland and are most exposed. Higher ground around the university colleges and the hills to the south carry substantially lower risk. The three example postcodes at the bottom of this article illustrate the range well: CB3 0DS (lower risk), CB4 1AA (medium), CB1 1BB (higher risk).

Subsidence is the risk most buyers do not check. With 35% of postcodes on probable shrink-swell clay and a further 54% on possible, this is not a fringe concern - it is the baseline for most Cambridge properties. Hot, dry summers dry the clay beneath buildings; wet winters expand it again. In a city with expensive housing stock, this movement cycle over time creates real structural and insurance consequences. A standard property search will flag this, but it is worth understanding before committing.

Heat will be the growing factor. Cambridge's combination of flat, inland geography and no coastal moderating effect means it is among the most exposed cities in England to projected increases in summer temperatures.

Check any Cambridge postcode at localrisk.co.uk for a full five-risk breakdown including subsidence and coastal erosion.

Check your postcode

You can check flood, heat, air quality, and subsidence risk for any UK postcode - free - at localrisk.co.uk. Cambridge's full council breakdown, with postcode-level comparisons, is at localrisk.co.uk/council/cambridge.

Try these Cambridge postcodes: 🟢 CB3 0DS - 🟡 CB4 1AA - 🔴 CB1 1BB

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; Open-Meteo Historical Weather Archive (ERA5 reanalysis, ECMWF), 30-year average 1991-2020; Met Office 1991-2020 station-based climate averages (Cambridge NIAB: 548mm rainfall, 1,494 hrs sunshine); ONS green space access data (2023). Analysis by LocalRisk. _Methodology: The WMO standard reference period is 1991-2020. Cambridge rainfall (548mm) and sunshine (1,494 hrs/yr) are from the Met Office NIAB station, 1991-2020. ERA5 overestimates precipitation in low-relief, low-rainfall areas of eastern England - ERA5 gives ~635mm for Cambridge vs the confirmed Met Office station figure of 548mm. Days above 25°C are used as the hot-day threshold to enable consistent cross-city comparison; the UK Heat Health Alert trigger is typically 28-30°C depending on region._