Merrimack River at Nashua, NH
River level and flood forecast · Hillsborough County
The river is 13.3 ft below flood stage (18 ft).
Forecast to hold near 4.8 ft through Thu, Oct 15, 8 AM.
The last 7 days and the forecast
NWS forecast issued Mon, Oct 12, 11:14 AM. Forecasts change as rain falls and as upstream water arrives.
Get flood alerts for this river
An email when the National Weather Service forecasts Merrimack River at Nashua to flood, when it floods, and when it's over.
Flood stages
| Major flood stage | 35 ft |
| Moderate flood stage | 26 ft |
| Flood stage | 18 ft |
| Action stage | 16 ft |
| Record crest (March 20, 1936) | 41.3 ft |
What floods at each level
From the National Weather Service, highest first.
- 40 ftThis is a disastrous...life threatening flood. This compares to the Great New England Flood of 1936. Follow the advice of local officials...and evacuate if told to do so.
- 35 ftThis is a major...life threatening flood event. The river has not reached this height since the Great New England flood of 1936. Major flooding will affect the communities of Merrimack and Litchfield through Nashua and Hudson. follow the advice of local officials...evacuate if told to do so. Stay away from the Merrimack River.
- 30 ftThis flood compares to the Hurricane of 1938 flood. This is a substantial flood event. Follow the directions of local officials...evacuate if told to do so. At this height the Merrimack River is moving very swiftly. Stay away from the river.
- 28 ftThe river has not reached this height since the Hurricane of 1938. This is a serious flood event. Follow the advice of local officials...evacuate if told to do so. At this height...the Merrimack River is moving very swiftly. Stay away from the river.
- 25 ftThe river has not reached this height since May 2006. This is a significant flood event. Follow the advice of local officials...evacuate if told to do so.
- 21 ftFlooding will occur in low lying areas from Litchfield and Merrimack...to Hudson and Nashua.
- 18 ftFlooding will begin in the lower lying sections of Hudson and Nashua as the river continues to climb above 18 feet.
Highest crests on record
- 41.3 ft — March 20, 1936
- 30.5 ft — September 23, 1938
- 26 ft — May 15, 2006
- 23.5 ft — April 17, 2007
- 22.4 ft — April 7, 1987
Recent crests: 18.81 ft (April 1, 2010) · 23.5 ft (April 17, 2007) · 12.5 ft (June 9, 2006) · 26 ft (May 15, 2006) · 14 ft (October 26, 2005)
Up and down the river, and nearby
Not an official source. River levels, forecasts, flood stages and impacts are from the National Weather Service (NSHN3); flow from the U.S. Geological Survey. Readings are provisional. In a flood, follow your local officials and the NWS at weather.gov.