Original analysis of NOAA, USGS, FEMA and Census data

Manchester freeze and flood data

Deep cold is less common than it was: Concord averaged 27.8 nights a year at or below zero in the 1970s and 7.6 over 2016-2025. The ice dam setup isn't: 21.3 thaw-and-refreeze days with snow on the ground in an average winter, and 22.6 over the last ten. Here is the record, by night, month, winter and ZIP code.

Every day of 2025 at Manchester Airport, colored by the overnight low. 5 nights reached zero or below, and 44 days never got above freezing.0°F or below1 to 1011 to 2021 to 3233 to 4546 to 6061+NOAA ACIS daily data, Manchester Airport (GHCN USW00014710).

Nights per year at or below 0°F, Concord

Source: NOAA ACIS daily data, Concord Municipal Airport (USW00014745), 1942 to 2025, the closest complete long record to Manchester.

Average days the high stayed at or below 32°F, by month

Source: NOAA ACIS, Manchester Airport, 2016-2025 average.

What we found

Fewer deep-freeze nights, but plenty of cold. Concord averaged 12.8 nights a year at or below 0°F over 1991-2020 and 7.6 over 2016-2025. Manchester Airport, a few degrees milder, averaged 2.6 subzero nights, 12.7 nights at or below 10°F and 26.4 days that never got above freezing over 2016-2025.
2025 was a cold year by recent standards. Manchester Airport had 5 subzero nights and 44 days at or below freezing; Concord had 15 subzero nights.
Ice dam weather hasn't faded with the snow. Snowfall at Concord averaged 67.6 inches a winter from 1991-92 to 2020-21 and 56.5 over the last ten winters, but thaw-and-refreeze days with 6 inches or more on the ground went from 21.3 to 22.6. February averages 9.6 of them.
The river floods in spring. The Merrimack at Goffs Falls passed its 11 foot minor flood stage in 33 of 88 years since 1936, most often in March and April when snowmelt meets rain. The record is 35.19 feet in March 1936; the highest since 1938 is 19.87 feet on May 15, 2006.
The heaviest rain came all at once. Manchester Airport recorded 8.52 inches in the three days ending May 15, 2006, the Mother's Day storm, and 4.99 inches in a single day on September 11, 1954.
Flood claims are few but large. 561 NFIP claims in the 21 ZIP codes we cover, $9.3 million paid, $22,400 per paid claim. 185 came in 2006 and 116 in 2007. About 45% of paid claims were rated outside the high-risk zones.

Ice dam weather: thaw-and-refreeze days with 6+ inches of snow on the ground, per winter

Source: NOAA ACIS, Concord Municipal Airport. A day counts when snow depth was 6 inches or more, the high reached 36°F and the low that night or the next fell to 28°F or below. Winters labelled by their first year.

Highest river stage each year, Merrimack River at Goffs Falls (feet)

Source: USGS annual peaks, site 01092000, 1936 to 2023. Flood stages: NWS gauge GOFN3 (minor 11, moderate 15, major 17 ft).

Flood insurance claims per year, the 21 ZIP codes we cover

Source: OpenFEMA NFIP redacted claims, by year of loss. Years with no claims are left out.

Highest crests, Merrimack at Goffs Falls

Date	Crest	NWS category
March 20, 1936	35.19 ft	Major
September 23, 1938	25.87 ft	Major
May 15, 2006	19.87 ft	Major
April 6, 1960	17.42 ft	Major
April 17, 2007	16.79 ft	Moderate
April 6, 1987	14.47 ft	Minor
March 28, 1953	13.90 ft	Minor
April 12, 1951	13.45 ft	Minor
June 1, 1984	13.36 ft	Minor
April 7, 1952	13.30 ft	Minor

NWS gauge GOFN3 historic crests. Flood stages: action 10 ft, minor 11, moderate 15, major 17.

Subzero nights per year, Concord, by decade

Decade	Average nights at or below 0°F
1940s	21.6
1950s	14
1960s	21.9
1970s	27.8
1980s	20.3
1990s	12.3
2000s	13.9
2010s	12.2

Coldest nights on record, Concord

Date	Low
February 16, 1943	-37°F
January 22, 1984	-33°F
January 18, 1957	-30°F
January 19, 1976	-30°F
January 19, 1971	-29°F
January 20, 1994	-28°F

Old brick mill buildings beside a rushing river in New Hampshire — Brick mill buildings on a New Hampshire river. In the West Side and downtown ZIP codes, 28% to 41% of homes were built before 1940 (Census ACS). Photo: Skyler Smith / Unsplash

Flood claims and housing by ZIP code

Housing age, building type and heating fuel shape what kind of water damage a ZIP code sees: old stacked buildings, oil heat and long winters on one end; newer single-family houses with finished basements on the other.

ZIP	Area	NFIP claims	Paid	Median year built	Built before 1940	2 to 4 units	Renter occupied	Heat with oil	Homes
03045	Goffstown	157	$2,999,518	1983	10%	3%	13%	54%	5,670
03054	Merrimack	61	$1,279,449	1985	4%	2%	11%	30%	11,151
03031	Amherst	53	$716,749	1978	11%	3%	8%	50%	4,578
03053	Londonderry	41	$407,694	1985	3%	4%	14%	45%	10,012
03038	Derry	37	$202,713	1983	7%	8%	30%	43%	14,507
03060	Nashua (downtown)	28	$214,047	1959	33%	30%	63%	10%	13,060
03062	Nashua (south)	27	$202,459	1983	2%	4%	29%	9%	12,215
03110	Bedford	26	$390,195	1990	5%	1%	17%	51%	8,387
03102	West Side	24	$94,249	1969	28%	26%	59%	23%	15,294
03106	Hooksett	23	$1,179,434	1988	5%	7%	20%	32%	5,696
03104	North End	14	$37,042	1960	33%	23%	46%	28%	15,685
03051	Hudson	12	$119,555	1983	5%	8%	17%	23%	10,217
03103	South Manchester	12	$125,507	1961	27%	36%	51%	28%	16,073
03064	Nashua (north end)	10	$96,021	1953	44%	25%	43%	9%	6,678
03109	East Side	9	$36,638	1987	6%	10%	23%	34%	4,288
03070	New Boston	8	$96,263	1989	13%	10%	12%	43%	2,124
03101	Downtown Manchester	8	$1,046,447	1972	41%	6%	91%	5%	2,041
03052	Litchfield	5	$13,230	1987	6%	2%	13%	42%	3,070
03063	Nashua (north)	3	$16,706	1981	2%	3%	37%	5%	6,807
03034	Candia	2	$11,884	1979	23%	3%	8%	64%	1,505
03032	Auburn	1	$32,600	1984	12%	2%	6%	49%	2,013

OpenFEMA FIMA NFIP redacted claims by reported ZIP code, all years, Hillsborough, Merrimack and Rockingham counties. Census ACS 2020-2024 5-year estimates by ZIP Code Tabulation Area (B25001, B25003, B25024, B25034, B25035, B25040). Click a column to sort.

Federal disaster declarations, Hillsborough County

Incident began	Event	Type
January 26, 2015	Severe Winter Storm And Snowstorm	Major disaster
February 8, 2013	Severe Winter Storm And Snowstorm	Major disaster
October 26, 2012	Hurricane Sandy	Emergency
October 29, 2011	Severe Storm	Emergency
October 29, 2011	Severe Storm And Snowstorm	Major disaster
August 26, 2011	Hurricane Irene	Emergency
March 14, 2010	Severe Storms And Flooding	Major disaster
February 23, 2010	Severe Winter Storm	Major disaster
December 11, 2008	Severe Winter Storm	Major disaster
December 11, 2008	Severe Winter Storm	Emergency
September 6, 2008	Severe Storms And Flooding	Major disaster
April 15, 2007	Severe Storms And Flooding	Major disaster
May 12, 2006	Severe Storms And Flooding	Major disaster
October 7, 2005	Severe Storms And Flooding	Major disaster
August 29, 2005	Hurricane Katrina Evacuation	Emergency
March 11, 2005	Record Snow	Emergency
January 22, 2005	Record And/Or Near Record Snow	Emergency
December 6, 2003	Snow	Emergency
February 17, 2003	Snow	Emergency
March 5, 2001	Snow	Emergency
June 12, 1998	Severe Storms And Flooding	Major disaster
January 7, 1998	Severe Ice Storm, Rains And High Winds	Major disaster
October 20, 1996	Fall Northeaster Rainstorm	Major disaster
March 13, 1993	Blizzards, High Winds & Record Snowfall	Emergency
August 18, 1991	Hurricane Bob & Severe Storms	Major disaster
August 7, 1990	Severe Storms & Flooding	Major disaster
March 30, 1987	Severe Storms & Flooding	Major disaster
July 29, 1986	Severe Storms, Flooding	Major disaster
July 11, 1973	Severe Storms & Flooding	Major disaster

OpenFEMA Disaster Declarations Summaries for Hillsborough County: floods, storms, snow and ice.

How we built this

Cold. Daily highs and lows from NOAA's Applied Climate Information System. Manchester Airport (GHCN USW00014710) has a full record only since 1998, so its numbers cover 2016-2025. Concord Municipal Airport (USW00014745), 18 miles up the Merrimack, has a complete record from 1942, so the long-run and decade figures come from there. Concord runs colder than Manchester; use it for the trend, Manchester for the level. Years missing more than 15 days are left out.

Ice dam days. Our definition, from Concord's daily data: snow depth of 6 inches or more, a high of 36°F or more, and a low of 28°F or less that night or the next. It is a weather setup, not a count of ice dams; whether one forms depends on the roof and the attic. Winters run July to June.

River. USGS annual peak stage at site 01092000 (Merrimack River near Goffs Falls, below Manchester), 1936 on, compared with the National Weather Service flood stages for gauge GOFN3 at the same point. Historic crests are from the NWS.

Claims and housing. OpenFEMA FIMA NFIP redacted claims for the three counties, kept where the reported ZIP is one of the 21 we cover. Census ACS 2020-2024 5-year estimates by ZIP Code Tabulation Area. The NFIP data covers flood insurance only; most water damage inside homes comes from pipes, roofs and appliances and is never in it.

Limits. Two airports and one river gauge don't describe every street. Use this to understand the area, not to judge a particular house.

Using this data. You may cite or republish these tables and charts (CC BY 4.0) as long as you link to this page.