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Weather & Climate in Groton, CT
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Groton experiences four distinct seasons with an average annual temperature of 51°F (11°C). Winters average 31°F in January while summers reach 72°F in July. The area gets 275 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 39.3 inches. Air quality is rated Good with a median AQI of 39. The city sits at an elevation of 34 feet.
Temperature
31°F Jan (-1°C)
72°F Jul (22°C)
| Annual Average | 51.4°F |
| 5% below US avg | |
| January Average | 31°F (-1°C) |
| July Average | 72°F (22°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 34 ft (10 m) |
| Area | 3.1 sq mi (8.0 km²) |
| Population Density | 3,033/sq mi |
| Coordinates | 41.3251°N, 72.0669°W |
| Timezone | America/New_York |
| County | Southeastern Connecticut Planning Region County |
| Nearest Airport | Rhode Island Tf Green International (PVD) 43 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 39.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 88.7 / 100 |
| Social Vulnerability | 26.8 / 100 |
| Community Resilience | 86.4 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Relatively High |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Moderate |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Moderate |
| Drought | Relatively Low |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
| Coastal Flood | Relatively Moderate |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
17 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 | 115 km | 10 km |
| Oct 2, 1994 | 1 km NW of Hardwick, Massachusetts | M3.3 | 116 km | 10 km |
| Jun 16, 2000 | 5 km NE of Granville, Massachusetts | M3.3 | 107 km | 10 km |
| Jan 12, 2015 | 0 km NE of Wauregan, Connecticut | M3.3 | 49 km | 5 km |
| Mar 22, 1996 | 2 km NE of Bristol, Rhode Island | M3.1 | 80 km | 12 km |
| Apr 9, 2019 | 63 km SSE of Sagaponack, New York | M3.0 | 103 km | 7 km |
| Oct 28, 1991 | 3 km WNW of Stamford, Connecticut | M3.0 | 130 km | 10 km |
| Mar 10, 1992 | 2 km SW of Napeague, New York | M2.8 | 37 km | 10 km |
| Oct 13, 1999 | 2 km E of Littleton Common, Massachusetts | M2.7 | 146 km | 2 km |
| Oct 11, 1990 | 5 km NNE of The Pinehills, Massachusetts | M2.7 | 141 km | 13 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 134 km | 9 km |
| Aug 14, 2014 | 6 km SW of Deep River Center, Connecticut | M2.7 | 36 km | 4 km |
| Jan 13, 2015 | 2 km E of Wauregan, Connecticut | M2.6 | 49 km | 9 km |
| Apr 22, 1996 | 3 km NE of North Westport, Massachusetts | M2.6 | 93 km | 5 km |
| Aug 22, 2000 | 2 km WSW of Brewster Hill, New York | M2.6 | 131 km | 7 km |
| Jun 7, 2002 | 3 km NNW of Hopedale, Massachusetts | M2.5 | 102 km | 5 km |
| Jan 23, 1990 | 3 km NNW of Boxborough, Massachusetts | M2.5 | 140 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Hurricane History
5 hurricanes (Category 1+) recorded within 500 km since 1980. Strongest on record: Category 2.
| Year | Name | Category | Max Wind | Closest |
| 2021 | Henri | Category 1 | 75 mph | 232 km |
| 2014 | Arthur | Category 1 | 75 mph | 235 km |
| 1996 | Edouard | Category 1 | 92 mph | 282 km |
| 1991 | Bob | Category 2 | 109 mph | 41 km |
| 1985 | Gloria | Category 1 | 86 mph | 88 km |
Source: NOAA IBTrACS (Category 1+, 1980-2026).
Tornado History
151 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 4 fatalities, 729 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 10, 1989 | EF4 | 70 km | 3.0 mi | 0 |
| Oct 3, 1979 | EF4 | 80 km | 11.3 mi | 3 |
| Jul 29, 1971 | EF3 | 86 km | 0.1 mi | 0 |
| May 24, 1962 | EF3 | 91 km | 11.6 mi | 1 |
| May 10, 1954 | EF3 | 74 km | 0.3 mi | 0 |
| Jun 9, 1953 | EF3 | 97 km | 28.0 mi | 0 |
| Aug 21, 1951 | EF3 | 46 km | 0.1 mi | 0 |
| Aug 18, 2023 | EF2 | 67 km | 9.1 mi | 0 |
| Aug 8, 1999 | EF2 | 52 km | 4.0 mi | 0 |
| Jul 10, 1989 | EF2 | 82 km | 0.2 mi | 0 |
| Jul 10, 1989 | EF2 | 93 km | 5.0 mi | 0 |
| Aug 7, 1986 | EF2 | 71 km | 4.0 mi | 0 |
| Jul 5, 1984 | EF2 | 83 km | 3.0 mi | 0 |
| Jul 24, 1975 | EF2 | 100 km | 0.3 mi | 0 |
| Sep 18, 1973 | EF2 | 76 km | 0.1 mi | 0 |
| Sep 6, 1973 | EF2 | 65 km | 3.3 mi | 0 |
| Aug 31, 1973 | EF2 | 71 km | 0.1 mi | 0 |
| Jun 12, 1973 | EF2 | 94 km | 1.5 mi | 0 |
| Aug 19, 1965 | EF2 | 79 km | 6.6 mi | 0 |
| Oct 12, 1962 | EF2 | 90 km | 4.1 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 | - | 105 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: CRESCENT BOW FIRE (1,068 acres, 2012).
| Year | Name | Acres Burned | Distance |
| 2012 | CRESCENT BOW FIRE | 1,068 | 80 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 31°F (-1°C) | 4.2 in | |
| February | 30°F (-1°C) | 3.6 in | Coldest |
| March | 38°F (3°C) | 4.4 in | |
| April | 47°F (8°C) | 4.3 in | |
| May | 56°F (14°C) | 3.8 in | |
| June | 65°F (19°C) | 3.6 in | |
| July | 72°F (22°C) | 3.3 in | Warmest, Driest |
| August | 71°F (22°C) | 4.1 in | |
| September | 64°F (18°C) | 3.9 in | |
| October | 54°F (12°C) | 3.9 in | |
| November | 45°F (7°C) | 4.6 in | Wettest |
| December | 35°F (2°C) | 4.3 in |
Groton has a seasonal temperature swing of 42°F / from 30°F in February to 72°F in July. Total annual precipitation is 47.9 inches, with November being the wettest month (4.6") and July the driest (3.3").