Weather & Climate in Northwest Harwinton, CT

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

Northwest Harwinton experiences four distinct seasons with an average annual temperature of 47°F (9°C). Winters average 24°F in January while summers reach 70°F in July. The area gets 271 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 54.3 inches (wetter than the 38-inch national average). The area receives 59.1 inches of snow annually, making winter weather a significant factor for residents. Air quality is rated Good with a median AQI of 39. The city sits at an elevation of 997 feet.

Temperature

24°F Jan (-4°C) 70°F Jul (21°C)

Annual Average	47.3°F
	12% below US avg
January Average	24°F (-4°C)
July Average	70°F (21°C)
Sunny Days	271 days/yr

Geography

Elevation	997 ft (304 m)
Area	8.8 sq mi (22.8 km²)
Population Density	359/sq mi
Coordinates	41.7764°N, 73.0795°W
Timezone	America/New_York
County	Northwest Hills Planning Region County
Nearest Airport	Bradley International (BDL) 23 miles away

Precipitation & Snow

Annual Rainfall 54.3"

43% above US avg

Snowfall 59.1"

Wettest Month (Nov) 4.37"

Driest Month (Feb) 3.43"

Air Quality

AQI Median	39.0
Rating	Good

Natural Hazard Risk

Overall Risk	Relatively Low
Risk Score	79.6 / 100
Social Vulnerability	12.8 / 100
Community Resilience	76.7 / 100

Hazard Breakdown

Tornado	Relatively Low
Hurricane	Relatively Moderate
Earthquake	Relatively Low
Wildfire	Very Low
Flood	Relatively Moderate
Hail	Relatively Low
Strong Wind	Relatively Low
Heat Wave	Very Low
Winter Weather	Relatively Low
Lightning	Relatively Low
Ice Storm	Relatively Moderate
Drought	Relatively Low
Cold Wave	Relatively Low
Landslide	Relatively Low
Avalanche	Very Low

Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

27 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.7.

Oct 2, 1994	6 km W of Hardwick, Massachusetts	M3.7	92 km	10 km
Jan 12, 2015	0 km NE of Wauregan, Connecticut	M3.3	98 km	5 km
Jun 16, 2000	5 km NE of Granville, Massachusetts	M3.3	42 km	10 km
Oct 2, 1994	1 km NW of Hardwick, Massachusetts	M3.3	96 km	10 km
Dec 13, 2009	15 km N of Medusa, New York	M3.2	123 km	10 km
Jul 24, 2007	12 km SSW of Altamont, New York	M3.1	126 km	15 km
May 18, 2009	15 km N of Medusa, New York	M3.1	123 km	9 km
Oct 28, 1991	3 km WNW of Stamford, Connecticut	M3.0	89 km	10 km
Aug 3, 2025	0 km W of Little Ferry, New Jersey	M3.0	131 km	10 km
Oct 21, 2009	15 km N of Medusa, New York	M2.9	122 km	7 km
Aug 5, 2025	1 km N of Hillsdale, New Jersey	M2.8	117 km	12 km
Mar 10, 1992	2 km SW of Napeague, New York	M2.8	120 km	10 km
Aug 27, 2011	5 km WSW of Altamont, New York	M2.8	131 km	22 km
Mar 22, 2009	9 km SW of Altamont, New York	M2.8	128 km	16 km
Apr 12, 1991	2 km ENE of North Castle, New York	M2.7	84 km	9 km
Aug 25, 2011	5 km WSW of Altamont, New York	M2.7	131 km	18 km
Feb 18, 2009	15 km N of Medusa, New York	M2.7	122 km	9 km
Feb 27, 2008	2 km SW of Central Bridge, New York	M2.7	147 km	6 km
Aug 14, 2014	6 km SW of Deep River Center, Connecticut	M2.7	68 km	4 km
Feb 20, 2009	15 km SSW of Altamont, New York	M2.7	122 km	8 km

Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Hurricane History

2 hurricanes (Category 1+) recorded within 500 km since 1980. Strongest on record: Category 2.

Year	Name	Category	Max Wind	Closest
1991	Bob	Category 2	104 mph	139 km
1985	Gloria	Category 1	86 mph	27 km

Source: NOAA IBTrACS (Category 1+, 1980–2026).

Tornado History

247 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 19 fatalities, 996 injuries.

Date	Rating	Distance	Path	Fatalities
May 29, 1995	EF4	55 km	11.5 mi	3
Jul 10, 1989	EF4	47 km	3.0 mi	0
Oct 3, 1979	EF4	36 km	11.3 mi	3
Aug 28, 1973	EF4	77 km	9.8 mi	4
Jun 1, 2011	EF3	45 km	37.6 mi	3
Jun 16, 1974	EF3	81 km	49.1 mi	0
Sep 13, 1971	EF3	70 km	0.5 mi	0
Jul 29, 1971	EF3	25 km	0.1 mi	0
Oct 3, 1970	EF3	97 km	35.4 mi	1
May 24, 1962	EF3	25 km	11.6 mi	1
May 10, 1954	EF3	53 km	0.3 mi	0
Aug 21, 1951	EF3	53 km	0.1 mi	0
May 15, 2018	EF2	59 km	1.2 mi	0
Jul 21, 2003	EF2	87 km	1.5 mi	0
Jul 21, 2003	EF2	86 km	1.3 mi	0
Jun 23, 2001	EF2	4 km	0.5 mi	0
May 18, 2000	EF2	74 km	0.2 mi	0
Aug 8, 1999	EF2	98 km	4.0 mi	0
Jul 3, 1997	EF2	75 km	1.5 mi	0
Jul 3, 1997	EF2	45 km	4.5 mi	0

Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Tsunami History

1 tsunami recorded within 500 km. Highest wave on record: 0.3 m (1 ft).

Year	Location	Cause	Max Wave	Deaths	Distance
1964	LONG ISLAND, NY	Meteorological	0.3 m	—	109 km

Source: NOAA/NCEI Historical Tsunami Database.

Wildfire History

1 wildfire (100+ acres) recorded within 100 km. Largest: UNNAMED (2,224 acres, 2008).

Year	Name	Acres Burned	Distance
2008	UNNAMED	2,224	100 km

Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month	Avg Temperature	Precipitation	Summary
January	24°F (-4°C)	3.7 in	Coldest
February	26°F (-3°C)	3.4 in	Driest
March	35°F (2°C)	4.0 in
April	46°F (8°C)	4.1 in
May	57°F (14°C)	4.3 in
June	65°F (18°C)	4.1 in
July	70°F (21°C)	4.0 in	Warmest
August	69°F (20°C)	4.2 in
September	61°F (16°C)	4.1 in
October	50°F (10°C)	4.0 in
November	40°F (5°C)	4.4 in	Wettest
December	30°F (-1°C)	4.2 in

Northwest Harwinton has a seasonal temperature swing of 46°F / from 24°F in January to 70°F in July. Total annual precipitation is 48.4 inches, with November being the wettest month (4.4") and February the driest (3.4").

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