Does Grantham flood?

What the Environment Agency's rivers-and-sea flood-risk data says about Grantham

Ordnance Survey places 124 postcodes in Grantham in the Environment Agency's rivers-and-sea flood-risk dataset (Risk of Flooding from Rivers and Sea). Each postcode is counted once, under the worst band any of its properties reaches; together they hold 1,422 properties in the EA dataset's likelihood bands.

This dataset covers flooding from rivers and the sea only — one of five flood sources. Surface water, groundwater, sewers and reservoirs are assessed separately, so a postcode missing from it is not proof that a place cannot flood. The band describes the land around properties (allowing for defences), not any single address and not today's conditions.

Rivers and live river levels near Grantham

Environment Agency gauges within 10 km of Grantham watch River Witham, Foston Beck, River Devon.

• Saltersford
  River Witham · 2.7 km away 0.12 m
  normal range · steady · 37 min ago
• Allington
  Foston Beck · 5.8 km away 0.07 m
  normal range · steady · 37 min ago
• Woolsthorpe
  River Devon · 8.0 km away 0.60 m
  normal range · 37 min ago
• Hougham
  River Witham · 8.6 km away 0.82 m
  normal range · steady · 37 min ago

Distances are from the middle of Grantham's at-risk postcodes. Tidal and structure gauges are shown as readings only — the tide and sluice gates move them, not floods. A gauge with no recent reading shows no level.

Flood warning areas near Grantham

7 Environment Agency flood warning areas lie within 10 km of Grantham. The EA has issued 147 flood warnings and alerts for them since 2006, most recently on 1 Mar 2026.

• Wider area at risk from the River Witham in Grantham from Dysart Park in the South of Grantham to Manthorpe in the North of Grantham
  no warning on record since 2006 0.6 km
• Areas near to the River Witham in Grantham from Dysart Park in the South of Grantham to Manthorpe in the North of Grantham
  3 warnings and alerts since 2006, latest Jan 2025 0.7 km
• Mow Beck near Alexandra Road and Harlaxton Road, and Barrowby Stream in the Winchester Road area of Grantham
  5 warnings and alerts since 2006, latest Jul 2021 1.0 km
• Isolated properties and villages near the River Witham from South Witham to Marston including South Witham, Colsterworth, Great Ponton, Little Ponton, Belton, Syston and Marston
  2 warnings and alerts since 2006, latest Jan 2025 5.6 km
• River Witham and its tributaries from South Witham to Claypole
  128 warnings and alerts since 2006, latest Mar 2026 6.8 km
• Areas near the Foston Beck in Sedgebrook and Allington and the A1 between Great Gonerby and Foston
  8 warnings and alerts since 2006, latest Jan 2025 7.1 km
• Areas near to the River Witham in Marston and Hougham
  1 warning or alert since 2006, latest Jan 2025 8.5 km

Recorded floods near Grantham

Floods whose mapped extent (EA Recorded Flood Outlines) reached within ~5 km of Grantham, most recent first. Records, not floods: no outline on the record is not evidence a place has not flooded. See them on the map →

• 4 Jan 2025 — LNA_2025_01_Fluvial_Grantham Main river
• 4 Jan 2025 — LNA_2025_01_Fluvial_Manthorpe Main river
• 5 Dec 2013 — LNA_2013_12_Tidal_Witham_Haven Sea
• 1 Jan 1922 — LNA_1922_08_Grantham Ordinary watercourse

Rainfall near Grantham

Grantham gets about 643 mm of rain a year on average (wettest month October, 65 mm; driest March, 39 mm). That is 45% drier than the UK as a whole, which averages 1,163 mm a year. Source: Met Office HadUK-Grid 1991–2020 (5 km grid), 1.9 km from the place centre.

The nearest rain gauge, Rainfall station (2.8 km away), recorded 0.0 mm in the last 24 hours and 42.2 mm in the last 7 days (latest reading 37 min ago).

At-risk postcodes in Grantham

Every postcode Ordnance Survey places in Grantham that appears in the EA's rivers-and-sea dataset, worst band first. Each links to its own flood-risk page.

High likelihood (40)

Medium likelihood (12)

Low likelihood (71)

Very low likelihood (1)

Postcode districts

Sources

FloodRadar summarises public flood data. It is not a flood-risk survey of any property, and it does not replace official GOV.UK flood warnings or the GOV.UK long-term flood risk service.