ZIP 01821
Middlesex County, MA

The heaviest year

2010 is the heaviest year on file: 68 paid claims, 23.9% of the ZIP's total. The rest is spread across the other 26 years on file. The largest named event in the record is March 2010 Nor'easter, with 67 claims.

5 of those claims — 1.8% — were filed since 2017. The bulk of this ZIP's record is older than that.

Named event	Paid claims	Share of record
March 2010 Nor'easter	67	23.6%
Not a named storm	27	9.5%

Where the claims sat on the map

Of the 265 claims here that record a rated flood zone, 70 — 26.4% — were on properties rated outside the mapped high-risk area, in a B, C or X zone. Being outside the high-risk zone has not meant much here. Flood insurance is not required outside the high-risk zone, and most properties there do not carry it — so these counts come from the minority who did.

The water near this ZIP

The closest gauges publishing official flood thresholds are Shawsheen River at Wilmington (2.3 mi), Concord River at Lowell (6.6 mi) and Merrimack River at Lowell (7.1 mi). A gauge describes one point on one river — it will not see street drainage, sewer backup, storm surge or flash flooding.

Read current gauge conditions for 01821 →

What this does not say

These are paid National Flood Insurance Program claims, nothing more. They count insured properties whose owners filed and were paid, so they are a floor on how often this ZIP has flooded — never a measure of how likely it is to flood next. Uninsured flooding leaves no trace here at all.

The figures are aggregates published by FEMA. No individual claim, address or policyholder appears on this page or in the data behind it. Nothing here is a forecast, a warning, or advice about insurance.