Photo: Bikeboy · CC BY-SA 2.0No home in Grays is at high or medium risk from rivers or the sea, but surface water reaches 44%
On the Environment Agency’s maps, which allow for flood defences, “high or medium” means at least a 1 in 100 chance of flooding from rivers or the sea in any year. Hazard risk puts Grays at A: #1 of 81 in Essex.
What stands out about Grays’s hazards
From the Environment Agency’s maps and records and the BGS radon atlas, below.
What Grays faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Rivers and the sea
Surface water
Past floods
Flood warnings
Radon
Grays grades A for hazard risk
Flood risk from rivers and the sea, against all UK towns.
The share of homes at high or medium risk from rivers and the sea, ranked against every UK town of 1,000 or more: fewer homes at risk is better. Towns with none at high or medium risk are ordered by their share at low risk, so they don’t all share one score. Surface water and radon aren’t graded: they are described below.
Where the water goes in Grays
Turn layers on and off. Blue is the risk from rivers and the sea; pink is where heavy rain collects. Both allow for flood defences.
No home in Grays is in the high or medium band for rivers or the sea. Surface-water risk is spread across the town, in dips, underpasses and along small streams, which is why more homes are exposed to it.
0% of Grays’s homes are at high or medium risk from rivers or the sea
The Environment Agency’s national map, allowing for defences. None are in the low-risk band.
Share of each UK town’s homes at high or medium risk from rivers and the sea. 35% of UK towns have none.
| # | Town | People | High or med. | |
|---|---|---|---|---|
| 1 | Smethwick West Midlands | 56,343 | 0% | |
| 2 | Bootle Merseyside | 53,722 | 0% | |
| 3 | Bloxwich West Midlands | 51,891 | 0% | |
| … | ||||
| 5 | Crosby Merseyside | 50,218 | 0% | |
| 6 | Ashton-under-Lyne Greater Manchester | 48,595 | 0% | |
| 7 | Grays Essex | 44,340 | 0% | |
| 8 | Borehamwood Hertfordshire | 39,760 | 0% | |
| 9 | Chadderton Greater Manchester | 37,602 | 0% | |
| … | ||||
| 169 | Exmouth Devon | 35,502 | 9.8% | |
| 170 | Caversham Berkshire | 33,038 | 13% | |
UK towns of 31,000 to 62,000 people.
The Environment Agency’s Risk of Flooding from Rivers and Sea (NaFRA2, June 2026) counts each postcode’s homes by band; the shares weight those postcodes by Census 2021 households. The EA counts include homes built since 2021.
44% of Grays’s homes are at high or medium risk from surface water
Surface water is rain that falls faster than drains and the ground can take it. It is mapped separately from rivers and the sea, and it is not in the Hazard risk Grade.
About 38% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 6.8% at medium risk: roughly 7,630 households. A further 7.8% face a low risk from surface water. That is more than 100% of UK towns.
Our estimate: every address in the town (ONS NSUL) read on the Environment Agency’s Risk of Flooding from Surface Water map (NaFRA2, 2025), each postcode’s share weighted by its Census 2021 households. Neither agency publishes a count of homes for surface water, so treat it as a guide; one street can differ from the next.
Grays has flooded in 1 recorded year since 1953
Every flood the Environment Agency has mapped inside Grays’s built-up area, newest first. The record is fullest for big river floods; small and surface-water floods are often missing.
- 1953January 1953: The sea came in48 hectares inside today’s built-up area · Coast Flood Essex
Floodwater covered 48 hectares of what is now Grays in 1953, the largest flood the record holds here (January).
689 of Grays’s households today live inside the outline of a recorded flood.
No flood warning or alert is in force for Grays · 0 warnings in 20 years
The Environment Agency has 2 flood warning areas and 1 alert area reaching into the town; warnings since the service began in 2006.
None of Grays’s 2 flood warning areas has had a flood warning since the service began in 2006.
Show the 3 warning and alert areas
| Area | Kind | Since 2006 | Now |
|---|---|---|---|
| The Thames estuary from Shellhaven, to and including Tilbury | Warning area | 0 | None |
| The Thames estuary from Grays to Purfleet-on-Thames, including West Thurrock | Warning area | 0 | None |
| The Essex coast from Fobbing to Purfleet-on-Thames | Alert area | 36 | None |
Environment Agency Historic Flood Warnings (first issues only, not updates; “flood watch” counted as an alert before 2011) and the real-time flood-monitoring API. Sign up for free warnings on GOV.UK or call Floodline, 0345 988 1188.
Parts of Grays are in radon Affected Areas, at the low end
Radon is a natural radioactive gas from the ground; long exposure raises the risk of lung cancer. The atlas gives the chance that a home in each 1 km square is above the UK action level (200 Bq/m³).
81% of Grays’s built-up area is in a radon Affected Area (1% of homes or more above the action level).
The squares are indicative: each takes the highest band found anywhere inside it, so most homes in a coloured square are below it. Only a three-month test in the home gives a real answer.
BGS/UKHSA Indicative Atlas of Radon in Great Britain, version 3. Check an address at UKradon.org.
Flood risk in the places around Grays
Share of homes at high or medium and at low risk from rivers and the sea. Tap a town for its page.
| Town | People | High or medium | Low | Hazard |
|---|---|---|---|---|
| Grays | 44,340 | 0% | 0% | A |
| Chadwell St Mary | 10,680 | 0% | 0% | A |
| Chafford Hundred and West Thurrock | 23,589 | under 0.1% | 0% | B |
| Tilbury | 14,187 | under 0.1% | 2.1% | B |
| Orsett | 1,428 | 0% | 0% | A |
| South Ockendon | 22,441 | 0% | 0% | A |
| Southfields | 1,167 | 0% | 0% | A |
| Swanscombe | 15,462 | 0% | 0% | A |
Get ready for what Grays faces
Free warnings, what to do in a cloudburst, and what to check before you move.
- Sign up free for Environment Agency flood warnings by text, call or email.
- Floodline: 0345 988 1188, 24 hours.
- Grays’s warning areas include The Thames estuary from Grays to Purfleet-on-Thames, including West Thurrock and The Thames estuary from Shellhaven, to and including Tilbury.
- Surface water rises in minutes, often with no warning issued: stay out of underpasses and dips.
- Keep the gullies and drains outside your home clear of leaves.
- Report a blocked road drain to the council.
- Test over three months, in a living room and a bedroom.
- Above 200 Bq/m³, a small sump and fan usually fixes it.
- New homes in radon areas are built with protection: basic from 3%, full from 10%.
- Check the address on GOV.UK’s long-term flood risk service: it gives rivers and sea and surface water separately.
- Ask whether the home has flooded or had a flood insurance claim; the TA6 property form asks the seller.
- Homes built before 2009 can get flood cover through Flood Re, the government-backed scheme; newer homes can’t.
- Check radon for the address on UKradon.org (a small fee) or ask the seller for a test result.
What this data can and can’t tell you
- Defences are counted. Both agencies’ maps allow for flood defences and the chance they are overtopped or fail, so a town behind a defence scheme can show few homes at high risk and many at low risk.
- Surface water is our estimate. Neither agency publishes a count of homes at risk from surface water, so we read each address on the map. A flat on a hill and a basement in a dip can share a postcode.
- Past floods are what was recorded. The flood outlines come from surveys, aerial photographs and reports; many small floods, and most surface-water floods, were never mapped.
- One town, many streets. Risk is street by street. Check a specific address on GOV.UK’s long-term flood risk service before you buy or rent.
Questions about flooding and hazards in Grays
Does Grays flood?
The last flood the Environment Agency recorded inside the town was in January 1953. 0% of homes are at high or medium risk from rivers and the sea on the Environment Agency’s maps, which allow for flood defences. About 44% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. Grays grades A for hazard risk against UK towns.
Which parts of Grays are at risk of flooding?
From rivers and the sea, the places the Environment Agency warns directly: The Thames estuary from Grays to Purfleet-on-Thames, including West Thurrock and The Thames estuary from Shellhaven, to and including Tilbury. Surface water can collect in low spots anywhere in the town. Check a specific address on GOV.UK’s long-term flood risk service.
When did Grays last flood?
The recorded flood outlines inside the town run from 1953 to 1953 (1 years); the largest was in 1953.
Is Grays at risk of surface water flooding?
About 38% of homes are at high risk and 6.8% at medium risk from surface water, against 0% at high or medium risk from rivers and the sea. Surface water floods come with little warning, and the agencies don’t issue warnings for them.
Is radon a problem in Grays?
81% of the town’s built-up area is in a radon Affected Area on the BGS/UKHSA atlas. Most homes are below it; a three-month test is the only way to know.
Are there flood warnings in Grays now?
No flood warning or alert was in force near Grays at 6 November 2026, 22:49. Live warnings are on GOV.UK’s Check for flooding service and Floodline, 0345 988 1188.
Contains Environment Agency information © Environment Agency and/or database right 2026. Contains British Geological Survey materials © UKRI 2026.
Sources: Environment Agency Risk of Flooding from Rivers and Sea, postcodes in areas at risk (June 2026); Natural Resources Wales Flood Risk Assessment Wales (May 2026); ONS Census 2021 households by postcode · Environment Agency Risk of Flooding from Surface Water (NaFRA2, 2025) and Natural Resources Wales Flood Risk Assessment Wales surface water and small watercourses, read at every address (ONS National Statistics UPRN Lookup, September 2026) and weighted by Census 2021 households by postcode · Environment Agency Recorded Flood Outlines and Natural Resources Wales historic flood map, inside the ONS 2022 built-up-area boundary · Environment Agency real-time flood-monitoring API · Environment Agency Historic Flood Warnings (January 2006 to June 2026) and flood warning and alert areas · BGS/UKHSA Indicative Atlas of Radon in Great Britain, version 3, by 1 km square · TownRatings grades: our own summary of the data, ranked against UK towns only. All under the Open Government Licence v3.0.
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.