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No official flood warning is active nearby and the closest river stations are within normal ranges.
Updated 2026-10-09 15:11:52 UTC · Official GOV.UK warnings · Flood preparation & help guide
Tewin is a village and civil parish in the East Hertfordshire district of Hertfordshire, England. It lies 3 miles (4.8 km) east of the village of Welwyn, which serves as its post town, 2 miles (3 km) north-east of Welwyn Garden City and 4 miles (6 km) north-west of Hertford. At the 2021 census, the parish had a population of 1,596.
Towns and villages near Tewin with a page of their own: the homes in a flood risk area there, the nearest river gauges, and recorded floods.
St Margarets · Stevenage · Stanstead Abbotts
Place names: Contains OS data © Crown copyright and database rights 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Contains National Statistics data © Crown copyright and database right 2026. Licensed under the Open Government Licence v3.0.
The nearest watercourse on the river map is the River Mimram, about 10 m from the middle of Tewin's gauges. It flows into the River Lea (River Lee) about 4.7 km downstream.
A gauge downstream shows water that has already passed this point; one upstream sees it first. Distances along the river are from the point on the River Mimram nearest the middle of Tewin's gauges. From Ordnance Survey’s river map (OS Open Rivers), which leaves out small streams, ditches and culverts, so a nearer one may exist. This describes where water goes on the map; it says nothing about flooding at any address. Contains OS data © Crown copyright and database rights 2026.
Tewin is monitored by 1 Environment Agency river level station on the River Mimram, in Hertfordshire. Water levels are updated every 15 minutes, providing real-time flood monitoring for the area.
The River Mimram is monitored by 1 station (Panshanger). Each station records water levels continuously, with data synced to FloodRadar every 5 minutes.
There are 8 Environment Agency flood warning areas within 10km of Tewin. When the EA issues a flood warning for any of these areas, it will appear on this page. These include: The River Mimram from Tewin to Hertford including Hertingfordbury; River Lee from Lemsford to Hertford including Welwyn Garden City, Hatfield and Mill Green; The River Beane at Hertford; The River Mimram at Whitwell, Welwyn, Tewin, Hertingfordbury and Hertford.
There are 3 storm overflows within 5km of Tewin. None of the 2 with a reporting monitor are currently discharging (1 has no live status right now). Enable "Sewage" on the map above to see their locations.
Each has its own page of live status and past discharges:
If flooding is forecast in Tewin, call Floodline on 0345 988 1188 for the latest information. Move valuables upstairs, turn off gas and electricity if safe to do so, and avoid walking or driving through flood water. Sign up for flood warnings on any station page above to receive email alerts when water levels rise. For emergency numbers, a preparation checklist and insurance guidance, see our flood help & preparation guide.
Tewin gets about 630 mm of rain a year on average (wettest month October, 68 mm; driest March, 39 mm). That is 46% drier than the UK as a whole, which averages 1,163 mm a year. See the rain gauges →
A thirty-year average for the area, not a forecast and not a flood risk on its own. Source: Met Office HadUK-Grid 1991–2020 (5 km grid), 1.0 km away. Average rainfall: HadUK-Grid v1.3.2, Met Office. Contains public sector information licensed under the Open Government Licence v3.0.
Floods whose mapped extent (EA Recorded Flood Outlines) reached within ~5 km of the town centre — most recent first. These are records of mapped extents, not a full list of floods. See them on the map →
Records, not floods: no outline on the record is not evidence a place has not flooded.
Current verdict: Normal. No official flood warning is active nearby and the closest river stations are within normal ranges.
Tewin has river level monitoring on River Mimram — 1 monitoring station in total.
Use the GOV.UK Check for Flooding service (check-for-flooding.service.gov.uk) or call Floodline on 0345 988 1188 (24 hours). You can also set up free FloodRadar email or browser alerts from any station page above.
Follow official advice: move valuables and vehicles to safety, never walk or drive through flood water, turn off gas and electricity if safe, and check on vulnerable neighbours. See our flood preparation guide at floodradar.co.uk/flood-help.
Yes — the Environment Agency's Recorded Flood Outlines dataset shows 11 recorded flood extents around the town centre since 1703, most recently in 1947. That is a count of mapped extents, not of separate floods. Records, not floods: no outline on the record is not evidence a place has not flooded. See the flood history link below.
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