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Merrimack River at Nashua

Highest listed crest 41.30 ftFlood stage 18.0 ft30 crests since 1936

The Merrimack River at Nashua crested at major flood stage 1 time among the 30 crests the National Weather Service lists from 1936 to 2010. The highest, 41.30 ft on March 20, 1936, was major flooding, 23.30 feet above flood stage. 5 other gauges on the Merrimack River crested above flood stage within a week of it, 5 at their own highest listed crest.

The gauge

Highest listed crest
41.30 ft
March 20, 1936
Flood stage
18.0 ft
Major flooding from 35.0 ft
Crests at major
1
20th of 34 gauges in New Hampshire
Most recent flood crest
April 1, 2010
18.81 ft, minor flooding
Location
Hillsborough County
Near Nashua (2.6 mi), Lowell (10.6 mi), Methuen (13.5 mi)

Flood stages

The thresholds the National Weather Service uses for this gauge today, and how many listed crests reached each.

Flood categories, Merrimack River at Nashua
Action stage16.04Jun 17, 1998The level at which the NWS or its partners begin to take action
Flood stage (minor)18.07Apr 1, 2010Minimal or no property damage, but possibly some public threat
Moderate flood stage26.02May 15, 2006Some inundation of structures and roads near the stream
Major flood stage35.01Mar 20, 1936Extensive inundation of structures and roads

Every listed crest

30 crests from 1936 to 2010. Filled: at or above flood stage. Hover a crest for its date and stage.

Listed crests at the Merrimack River at Nashua, 1936 to 2010 01020304050ft Flood stage 18.0 ftMajor 35.0 ft Mar 20, 1936: 41.30 ft, major floodingSep 23, 1938: 30.50 ft, moderate floodingApr 14, 1940: 18.10 ft, minor floodingMar 22, 1945: 13.60 ft, below flood stageMar 23, 1948: 15.30 ft, below flood stageApr 4, 1951: 17.00 ft, action stageApr 4, 1952: 17.00 ft, action stageMar 28, 1953: 18.40 ft, minor floodingApr 5, 1967: 13.50 ft, below flood stageMar 28, 1968: 14.20 ft, below flood stageApr 23, 1969: 15.60 ft, below flood stageFeb 12, 1970: 14.00 ft, below flood stageApr 22, 1972: 13.80 ft, below flood stageApr 7, 1987: 22.40 ft, minor floodingApr 29, 1988: 13.30 ft, below flood stageApr 1, 1993: 16.20 ft, action stageApr 13, 1993: 15.50 ft, below flood stageNov 15, 1995: 9.40 ft, below flood stage; 25,257 cubic feet per secondApr 18, 1996: 19.00 ft, minor flooding; 37,900 cubic feet per secondOct 22, 1996: 18.10 ft, minor flooding; 57,800 cubic feet per secondApr 20, 1997: 15.60 ft, below flood stageJun 17, 1998: 17.00 ft, action stageApr 1, 2003: 14.00 ft, below flood stageApr 2, 2004: 14.50 ft, below flood stageOct 10, 2005: 13.00 ft, below flood stageOct 26, 2005: 14.00 ft, below flood stageMay 15, 2006: 26.00 ft, moderate floodingJun 9, 2006: 12.50 ft, below flood stageApr 17, 2007: 23.50 ft, minor floodingApr 1, 2010: 18.81 ft, minor flooding Highest, 41.30 ft, Mar 20, 1936 19401950196019701980199020002010

Crests at or above flood stage, by decade

Crests at or above flood stage per decade, Merrimack River at Nashua 1930s: 2 2 1940s: 1 1950s: 1 1960s: 0 1970s: 0 1980s: 1 1990s: 2 2000s: 2 2010s: 1 1930s1940s1950s1960s1970s1980s1990s2000s2010s
  1. These are the crests the local National Weather Service office lists for the gauge: the highest on record and recent crests. Lesser floods between them may be missing, so counts by decade are a floor.
  2. Categories use today's flood stages. Levees, dams and channel changes since a crest can make old and new stages not directly comparable.

Highest crests

Highest listed crests, Merrimack River at Nashua
1Mar 20, 193641.30+23.30Major—
2Sep 23, 193830.50+12.50Moderate—
3May 15, 200626.00+8.00Moderate—
4Apr 17, 200723.50+5.50Minor—
5Apr 7, 198722.40+4.40Minor—
6Apr 18, 199619.00+1.00Minor37,900
7Apr 1, 201018.81+0.81Minor—
8Mar 28, 195318.40+0.40Minor—
9Apr 14, 194018.10+0.10Minor—
10Oct 22, 199618.10+0.10Minor57,800
11Apr 4, 195117.00−1.00Action—
12Apr 4, 195217.00−1.00Action—
13Jun 17, 199817.00−1.00Action—
14Apr 1, 199316.20−1.80Action—
15Apr 23, 196915.60−2.40Below flood stage—
16Apr 20, 199715.60−2.40Below flood stage—
17Apr 13, 199315.50−2.50Below flood stage—
18Mar 23, 194815.30−2.70Below flood stage—
19Apr 2, 200414.50−3.50Below flood stage—
20Mar 28, 196814.20−3.80Below flood stage—
21Feb 12, 197014.00−4.00Below flood stage—
22Apr 1, 200314.00−4.00Below flood stage—
23Oct 26, 200514.00−4.00Below flood stage—
24Apr 22, 197213.80−4.20Below flood stage—
25Mar 22, 194513.60−4.40Below flood stage—
26Apr 5, 196713.50−4.50Below flood stage—
27Apr 29, 198813.30−4.70Below flood stage—
28Oct 10, 200513.00−5.00Below flood stage—
29Jun 9, 200612.50−5.50Below flood stage—
30Nov 15, 19959.40−8.60Below flood stage25,257

The worst floods along the Merrimack River

For this gauge's highest crests, the other gauges on the Merrimack River that crested above flood stage within a week.

March 20, 1936: 41.30 ft here, major flooding

  • LowellMA · Mar 20, 1936 · 68.40 ft · Major · its highest
  • Franklin Jct.NH · Mar 19, 1936 · 36.40 ft · Major · its highest
  • Goffs FallsNH · Mar 20, 1936 · 35.19 ft · Major · its highest
  • ConcordNH · Mar 20, 1936 · 26.20 ft · Major · its highest
  • HaverhillMA · Mar 20, 1936 · 25.75 ft · Major · its highest

September 23, 1938: 30.50 ft here, moderate flooding

  • LowellMA · Sep 23, 1938 · 60.57 ft · Major
  • Franklin Jct.NH · Sep 22, 1938 · 29.50 ft · Major
  • Goffs FallsNH · Sep 23, 1938 · 25.87 ft · Major
  • ConcordNH · Sep 22, 1938 · 23.00 ft · Major

May 15, 2006: 26.00 ft here, moderate flooding

  • LowellMA · May 15, 2006 · 58.84 ft · Major
  • Goffs FallsNH · May 15, 2006 · 19.87 ft · Major
  • HaverhillMA · May 15, 2006 · 17.05 ft · Major
  • ConcordNH · May 15, 2006 · 15.12 ft · Minor

Gauges on the Merrimack River

Flood gauges sharing the river's name, linked within 80 miles of one another.

Flood gauges on the Merrimack River
Franklin Jct.NH16.036.40 ft, Mar 19, 19363
ConcordNH14.026.20 ft, Mar 20, 19363
Goffs FallsNH11.035.19 ft, Mar 20, 19364
Nashua this gaugeNH18.041.30 ft, Mar 20, 19361
LowellMA52.068.40 ft, Mar 20, 19365
LawrenceMA24.025.37 ft, Dec 20, 20230
HaverhillMA11.025.75 ft, Mar 20, 19363

Other gauges in Hillsborough County

Flood gauges in Hillsborough County
Peterborough5.515.00 ft, Sep 21, 19381
Goffs Falls11.035.19 ft, Mar 20, 19364
Goffstown9.017.52 ft, Sep 21, 19384
Merrimack9.016.20 ft, Mar 19, 19361
Milford9.012.49 ft, Apr 16, 20071

Hillsborough County: every hazard · River floods across the country · New Hampshire

NOAA National Water Prediction Service, gauge NSHN3, retrieved October 30, 2026. Stages in feet on the gauge's own datum, not elevation. Crests are as the National Weather Service lists them; preliminary values may be revised.