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Milk Street, St Helens Town CentrePhoto: Gary Rogers · CC BY-SA 2.0
C+Hazard risk Grade
Flood & hazards in St Helens · Environment Agency

In St Helens, heavy rain puts more homes at risk than rivers or the sea: 4%, against 0.5%

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. For hazard risk, St Helens grades C+: #23 of 25 in Merseyside.

10flood warnings since 200694%in a radon Affected Area
In brief

What stands out about St Helens’s hazards

From the Environment Agency’s maps and records and the BGS radon atlas, below.

Rain, more than the river4% of homes sit where heavy rain can flood the streets, against 0.5% at risk from rivers and the sea.The Windle Brook ran its 5th-highest in January 20251.96 m at Rivington Road on 1 January 2025, 0 cm under the record set in 2025.10 flood warnings since 2006For the parts of St Helens the Environment Agency warns directly; the most recent on 20 September 2025.Radon in parts42% of the city is in 1 km squares where 5% or more of homes may be above the radon action level.
By hazard

What St Helens faces

Each hazard against its own yardstick; meters run from low to high on that yardstick.

Rivers and the sea

0.5%of homes at high or medium risk
More than the typical UK town · more than 58% of towns
236 homes by the EA’s own count

Surface water

4%of homes at high or medium risk
More than 57% of UK towns
Rivers and sea: 0.5%

Past floods

1years with a recorded flood
Last recorded: December 2015
10 households inside past outlines

The Windle Brook

1.24 mhighest in winter 2025–26 at Rivington Road
15th-highest of 23 winters
Record 1.96 m, January 2025

Flood warnings

10flood warnings since 2006
40 flood alerts for the wider area
Last warning 20 September 2025

Radon

94%of the city in a radon Affected Area
Highest band here: 10–30% of homes
42% in squares of 5% or more
Not on this page: coastal erosion, subsidence and shrink-swell ground (the British Geological Survey licenses it), groundwater flooding and reservoir failure.
Hazard risk Grade

St Helens grades C+ for hazard risk

Flood risk from rivers and the sea, against all UK towns.

Homes at high or medium flood risk (0.5%)Fewer than 42% of 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.

Flood map

Where the water goes in St Helens

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.

Recorded flood: 2015© OpenStreetMap contributors · EA NaFRA2
HighMediumLowrivers & seaHighMediumLowsurface waterSt Helens’s built-up area

The river and sea risk follows the River Sankey, the Rainford Brook and the Sutton Mill Brook. Surface-water risk is spread across the city, in dips, underpasses and along small streams, which is why more homes are exposed to it.

Rivers and the sea

0.5% of St Helens’s homes are at high or medium risk from rivers or the sea

The Environment Agency’s national map, allowing for defences. A further 1.4% are at low risk.

High risk0.3%of homes · 1 in 30 a year or more159 homes, EA count
Medium risk0.2%of homes · 1 in 30 to 1 in 10077 homes, EA count
Low risk1.4%of homes · 1 in 100 to 1 in 1,000730 homes, EA count
Where St Helens sits among 3,735 UK towns
35%None
23%Under 0.5%St Helens
9%0.5–1%
11%1–2%
11%2–5%
5%5–10%
3%10–20%
2%20% +

Share of each UK town’s homes at high or medium risk from rivers and the sea. 35% of UK towns have none; St Helens has more than 58% of towns.

Towns its size: 29th of 74 from the fewest homes at risk
#TownPeopleHigh or med.
1Oldham Greater Manchester110,7220%
2Birkenhead Merseyside109,8540%
3Kensington and Chelsea London143,348under 0.1%
…
27Hartlepool County Durham88,0010.4%
28Woking Surrey75,6550.5%
29St Helens Merseyside107,6840.5%
30Tamworth Staffordshire76,0740.5%
31Burnley Lancashire78,2660.6%
…
73Lincoln Lincolnshire104,5536%
74Grimsby Lincolnshire85,9158.9%

UK towns of 75,000 to 151,000 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.

Surface water

Heavy rain puts about 8.4 times as many St Helens homes at risk as rivers and the sea do

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.

Surface water4%
Rivers and the sea0.5%
0%7%14% of homes

About 2% of homes are at high risk of surface-water flooding (a 1 in 30 chance or more each year) and 2% at medium risk: roughly 1,950 households. A further 6.5% face a low risk from surface water. That is more than 57% of UK towns.

~1,950
households at high or medium risk
6.5%
of homes at low risk
57%
of UK towns have a smaller share
59,155
addresses read on the map

Our estimate: every address in the city (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.

Flood history

St Helens has flooded in 1 recorded year since 2015

Every flood the Environment Agency has mapped inside St Helens’s built-up area, newest first. The record is fullest for big river floods; small and surface-water floods are often missing.

  1. 2015December 2015: River flooding recordedUnder 1 hectare inside today’s built-up area

10 of St Helens’s households today live inside the outline of a recorded flood.

River levels

The Windle Brook in January 2025 rose to its 5th-highest level since 2001

The highest level each winter (October to September) at the Environment Agency’s Rivington Road gauge, since 2001. The river normally runs between 0.00 m and 1.50 m here.

Highest level each winter, metres
Winter 2001–02: highest 4.00 m on 16 August 2002 · 3 days above the normal rangeWinter 2002–03: highest 4.00 m on 16 October 2002 · 2 days above the normal rangeWinter 2003–04: highest 1.28 m · 0 days above the normal rangeWinter 2004–05: highest 1.32 m · 0 days above the normal rangeWinter 2005–06: highest 1.30 m · 0 days above the normal rangeWinter 2006–07: highest 3.87 m on 26 February 2007 · 3 days above the normal rangeWinter 2007–08: highest 1.53 m · 2 days above the normal rangeWinter 2008–09: highest 0.92 m · 0 days above the normal rangeWinter 2009–10: highest 1.08 m · 0 days above the normal rangeWinter 2010–11: highest 1.02 m · 0 days above the normal rangeWinter 2011–12: highest 1.28 m · 0 days above the normal rangeWinter 2012–13: highest 1.16 m · 0 days above the normal rangeWinter 2015–16: highest 1.27 m · 0 days above the normal rangeWinter 2016–17: highest 0.99 m · 0 days above the normal rangeWinter 2017–18: highest 0.98 m · 0 days above the normal rangeWinter 2018–19: highest 1.12 m · 0 days above the normal rangeWinter 2019–20: highest 1.55 m on 9 February 2020 · 1 days above the normal rangeWinter 2020–21: highest 1.63 m on 20 January 2021 · 1 days above the normal rangeWinter 2021–22: highest 1.19 m · 0 days above the normal rangeWinter 2022–23: highest 1.44 m · 0 days above the normal rangeWinter 2023–24: highest 1.52 m · 1 days above the normal rangeWinter 2024–25: highest 1.96 m on 1 January 2025 · 2 days above the normal rangeWinter 2025–26: highest 1.24 m · 0 days above the normal range’01–02’02–03’06–07Record 1.96 m, 2025Top of normal range
2001–022025–26
The highest days on record
  • 16 August 20024.00 m
  • 16 October 20024.00 m
  • 26 February 20073.87 m
  • 11 January 20022.91 m
  • 1 January 20251.96 m
  • 18 January 20071.70 m

The Windle Brook has topped its normal range on 15 days since 2001, most in the winters of 2001–02 and 2006–07. By its highest day, the winter of 2025–26 was the 15th-highest of the 23.

Environment Agency Hydrology API, Rivington Road (station 694121), daily maximum level; the record and normal range from the EA’s stage scale. Live river levels are on GOV.UK’s Check for flooding.

Flood warnings

No flood warning or alert is in force for St Helens · 10 warnings in 20 years

The Environment Agency has 5 flood warning areas and 1 alert area reaching into the city; warnings since the service began in 2006.

Now: no flood warnings or alerts for St Helens (checked 6 November 2026, 00:52). Check for flooding on GOV.UK →
Warnings and alerts each year for areas in St Helens
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Flood warning (flooding expected)Flood alert (flooding possible)

Of the 10 warnings, 4 were for Rainford Brook at Moss Bank and 3 for Sutton Mill Brook at Sutton Leach. 2025 had the most warnings (4); 2019 the most alerts (6).

The most recent warning was on 20 September 2025.

Show the 6 warning and alert areas
AreaKindSince 2006Now
Rainford Brook at Moss BankWarning area4None
Sutton Mill Brook at Sutton LeachWarning area3None
Sutton Brook at Moss NookWarning area3None
Windle Brook at Dentons GreenWarning area0None
Mill Brook at EcclestonWarning area0None
River Sankey catchment with St Helens and WarringtonAlert area40None

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.

Radon

Parts of St Helens are in radon Affected Areas, up to the 10–30% band

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).

SJ4795: 1–3% of homes above the action levelSJ4796: 10–30% of homes above the action levelSJ4892: Under 1% of homes above the action levelSJ4893: Under 1% of homes above the action levelSJ4894: Under 1% of homes above the action levelSJ4895: 1–3% of homes above the action levelSJ4896: 10–30% of homes above the action levelSJ4897: 10–30% of homes above the action levelSJ4898: 1–3% of homes above the action levelSJ4992: 1–3% of homes above the action levelSJ4993: 3–5% of homes above the action levelSJ4994: 3–5% of homes above the action levelSJ4995: 1–3% of homes above the action levelSJ4996: 3–5% of homes above the action levelSJ4997: Under 1% of homes above the action levelSJ4998: 1–3% of homes above the action levelSJ5091: Under 1% of homes above the action levelSJ5092: 3–5% of homes above the action levelSJ5093: 3–5% of homes above the action levelSJ5094: 10–30% of homes above the action levelSJ5095: 10–30% of homes above the action levelSJ5096: 3–5% of homes above the action levelSJ5097: 3–5% of homes above the action levelSJ5190: Under 1% of homes above the action levelSJ5191: 3–5% of homes above the action levelSJ5192: 3–5% of homes above the action levelSJ5193: 3–5% of homes above the action levelSJ5194: 10–30% of homes above the action levelSJ5195: 10–30% of homes above the action levelSJ5196: 10–30% of homes above the action levelSJ5197: 1–3% of homes above the action levelSJ5198: 1–3% of homes above the action levelSJ5290: Under 1% of homes above the action levelSJ5291: 3–5% of homes above the action levelSJ5292: 3–5% of homes above the action levelSJ5293: 5–10% of homes above the action levelSJ5294: 10–30% of homes above the action levelSJ5295: 10–30% of homes above the action levelSJ5296: 10–30% of homes above the action levelSJ5297: 1–3% of homes above the action levelSJ5298: 1–3% of homes above the action levelSJ5391: Under 1% of homes above the action levelSJ5392: Under 1% of homes above the action levelSJ5393: 10–30% of homes above the action levelSJ5394: 10–30% of homes above the action levelSJ5395: 10–30% of homes above the action levelSJ5396: 10–30% of homes above the action levelSJ5397: 10–30% of homes above the action levelSJ5493: 3–5% of homes above the action levelSJ5494: 3–5% of homes above the action levelSJ5495: 10–30% of homes above the action levelSJ5594: 10–30% of homes above the action level© OpenStreetMap contributors · BGS/UKHSA
Under 1%1–3%3–5%5–10%10–30%
Share of the city’s area in each band
Under 1% of homes6%
1–3% of homes16%
3–5% of homes36%
5–10% of homes4%
10–30% of homes38%

94% of St Helens’s built-up area is in a radon Affected Area (1% of homes or more above the action level), and 42% in squares of 5% or more, mostly on the north-east side of the city.

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.

Neighbours

Flood risk in the places around St Helens

Share of homes at high or medium and at low risk from rivers and the sea. Tap a town for its page.

Prescot: Hazard risk BHaydock: Hazard risk B+Billinge: Hazard risk ABurtonwood: Hazard risk B+Cronton: Hazard risk ARainford: Hazard risk B+Newton-le-Willows: Hazard risk B+PrescotHaydockBillingeBurtonwoodCrontonRainfordNewton-le-WillowsSt Helens
ABCD
TownPeopleHigh or mediumLowHazard
St Helens107,6840.5%1.4%C+
Prescot39,227under 0.1%0.2%B
Haydock16,1430%0.8%B+
Billinge4,9630%0%A
Burtonwood3,5040%0.3%B+
Cronton1,2340%0%A
Rainford5,5730%0.1%B+
Newton-le-Willows24,6510%0.3%B+

St Helens has more homes at high or medium risk than any neighbour in the table.

Be ready

Get ready for what St Helens faces

Free warnings, what to do in a cloudburst, and what to check before you move.

Get the warnings
  • Sign up free for Environment Agency flood warnings by text, call or email.
  • Floodline: 0345 988 1188, 24 hours.
  • St Helens’s warning areas include Windle Brook at Dentons Green and Mill Brook at Eccleston.
Sign up ↗
In a cloudburst
  • 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.
Radon
  • 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%.
UKradon ↗
Before you buy or rent in St Helens
  • 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.
How to read these numbers

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.

Check the long-term flood risk for an address on GOV.UK →

Questions about flooding and hazards in St Helens

Does St Helens flood?

The last flood the Environment Agency recorded inside the city was in December 2015. 0.5% 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 4% of homes are at high or medium risk from surface water, when heavy rain overwhelms the drains. St Helens grades C+ for hazard risk against UK towns.

Which parts of St Helens are at risk of flooding?

From rivers and the sea, the places the Environment Agency warns directly: Rainford Brook at Moss Bank, Sutton Mill Brook at Sutton Leach, Sutton Brook at Moss Nook and Windle Brook at Dentons Green. Surface water can collect in low spots anywhere in the city. Check a specific address on GOV.UK’s long-term flood risk service.

When did St Helens last flood?

The recorded flood outlines inside the city run from 2015 to 2015 (1 years); the largest was in 2015. Flood warnings have been issued for parts of the city since 2006, most recently on 20 September 2025.

Is St Helens at risk of surface water flooding?

About 2% of homes are at high risk and 2% at medium risk from surface water, against 0.5% 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 St Helens?

94% of the city’s built-up area is in a radon Affected Area on the BGS/UKHSA atlas, and 42% is in 1 km squares where 5% or more of homes may be above the action level. Most homes are below it; a three-month test is the only way to know.

Are there flood warnings in St Helens now?

No flood warning or alert was in force near St Helens at 6 November 2026, 00:52. 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 Hydrology API (daily maximum river level) and flood-monitoring stage scales · 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.