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Weather & Climate in Cornwall, CT
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Cornwall experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 25°F in January while summers reach 71°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 46.9 inches (wetter than the 38-inch national average). Air quality is rated Good with a median AQI of 39. The city sits at an elevation of 704 feet.
Temperature
25°F Jan (-4°C)
71°F Jul (22°C)
| Annual Average | 48.4°F |
| 10% below US avg | |
| January Average | 25°F (-4°C) |
| July Average | 71°F (22°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 704 ft (215 m) |
| Area | 0.6 sq mi (1.5 km²) |
| Population Density | 116/sq mi |
| Coordinates | 41.8443°N, 73.3327°W |
| Timezone | America/New_York |
| County | Northwest Hills Planning Region County |
| Nearest Airport | Hudson Valley Regional (POU) 32 miles away |
Precipitation & Snow
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
28 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.0.
| Jun 17, 1991 | 7 km NE of Worcester, New York | M4.0 | 141 km | 5 km |
| Oct 2, 1994 | 6 km W of Hardwick, Massachusetts | M3.7 | 104 km | 10 km |
| Jun 16, 2000 | 5 km NE of Granville, Massachusetts | M3.3 | 51 km | 10 km |
| Oct 2, 1994 | 1 km NW of Hardwick, Massachusetts | M3.3 | 108 km | 10 km |
| Jan 12, 2015 | 0 km NE of Wauregan, Connecticut | M3.3 | 119 km | 5 km |
| Dec 13, 2009 | 15 km N of Medusa, New York | M3.2 | 103 km | 10 km |
| Jul 24, 2007 | 12 km SSW of Altamont, New York | M3.1 | 106 km | 15 km |
| May 18, 2009 | 15 km N of Medusa, New York | M3.1 | 103 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 | 125 km | 10 km |
| Feb 3, 2009 | 1 km ESE of Victory Gardens, New Jersey | M3.0 | 147 km | 0 km |
| Oct 21, 2009 | 15 km N of Medusa, New York | M2.9 | 103 km | 7 km |
| Aug 5, 2025 | 1 km N of Hillsdale, New Jersey | M2.8 | 109 km | 12 km |
| Mar 10, 1992 | 2 km SW of Napeague, New York | M2.8 | 141 km | 10 km |
| Aug 27, 2011 | 5 km WSW of Altamont, New York | M2.8 | 112 km | 22 km |
| Mar 22, 2009 | 9 km SW of Altamont, New York | M2.8 | 109 km | 16 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 82 km | 9 km |
| Aug 25, 2011 | 5 km WSW of Altamont, New York | M2.7 | 112 km | 18 km |
| Feb 18, 2009 | 15 km N of Medusa, New York | M2.7 | 103 km | 9 km |
| Feb 20, 2009 | 15 km SSW of Altamont, New York | M2.7 | 103 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 | 161 km |
| 1985 | Gloria | Category 1 | 86 mph | 45 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tornado History
236 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 25 fatalities, 1,021 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 29, 1995 | EF4 | 40 km | 11.5 mi | 3 |
| Jul 10, 1989 | EF4 | 63 km | 3.0 mi | 0 |
| Oct 3, 1979 | EF4 | 55 km | 11.3 mi | 3 |
| Aug 28, 1973 | EF4 | 64 km | 9.8 mi | 4 |
| Jun 1, 2011 | EF3 | 56 km | 37.6 mi | 3 |
| Jun 16, 1974 | EF3 | 61 km | 49.1 mi | 0 |
| Sep 13, 1971 | EF3 | 77 km | 0.5 mi | 0 |
| Jul 29, 1971 | EF3 | 40 km | 0.1 mi | 0 |
| May 24, 1962 | EF3 | 37 km | 11.6 mi | 1 |
| May 10, 1954 | EF3 | 72 km | 0.3 mi | 0 |
| Aug 21, 1951 | EF3 | 75 km | 0.1 mi | 0 |
| May 15, 2018 | EF2 | 48 km | 1.2 mi | 0 |
| Jul 12, 2006 | EF2 | 97 km | 10.1 mi | 0 |
| Jul 21, 2003 | EF2 | 66 km | 1.5 mi | 0 |
| Jul 21, 2003 | EF2 | 69 km | 1.3 mi | 0 |
| Jun 23, 2001 | EF2 | 18 km | 0.5 mi | 0 |
| May 18, 2000 | EF2 | 53 km | 0.2 mi | 0 |
| May 31, 1998 | EF2 | 86 km | 8.0 mi | 0 |
| Jul 3, 1997 | EF2 | 62 km | 1.5 mi | 0 |
| Jul 3, 1997 | EF2 | 37 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 | — | 118 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
9 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (23,000 acres, 1985).
| Year | Name | Acres Burned | Distance |
| 1985 | UNNAMED | 23,000 | 97 km |
| 2015 | ROOSA GAP | 2,747 | 93 km |
| 2008 | UNNAMED | 2,224 | 79 km |
| 2016 | SAMS POINT FIRE-VERKEERDER FIRE | 1,929 | 86 km |
| 2021 | EAST MOUNTAIN | 964 | 99 km |
| 2006 | CHERRYTOWN FIRE | 943 | 86 km |
| 1988 | UNNAMED | 833 | 94 km |
| 2016 | SHERWOOD | 642 | 98 km |
| 2024 | WHITEHOUSE | 607 | 93 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 25°F (-4°C) | 3.7 in | |
| February | 24°F (-5°C) | 3.4 in | Coldest, Driest |
| March | 33°F (0°C) | 3.9 in | |
| April | 44°F (7°C) | 4.1 in | |
| May | 55°F (13°C) | 4.5 in | Wettest |
| June | 63°F (17°C) | 4.2 in | |
| July | 71°F (22°C) | 4.2 in | Warmest |
| August | 67°F (19°C) | 4.3 in | |
| September | 59°F (15°C) | 4.1 in | |
| October | 48°F (9°C) | 3.9 in | |
| November | 38°F (3°C) | 4.4 in | |
| December | 27°F (-3°C) | 4.1 in |
Cornwall has a seasonal temperature swing of 48°F / from 24°F in February to 71°F in July. Total annual precipitation is 48.7 inches, with May being the wettest month (4.5") and February the driest (3.4").