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Weather & Climate in Derby, CT
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Derby experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 27°F in January while summers reach 73°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 52.0 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 8 feet.
Temperature
27°F Jan (-3°C)
73°F Jul (23°C)
| Annual Average | 50.2°F |
| 7% below US avg | |
| January Average | 27°F (-3°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 271 days/yr |
Geography
| Elevation | 8 ft (2 m) |
| Area | 5.1 sq mi (13.1 km²) |
| Population Density | 2,442/sq mi |
| Coordinates | 41.3261°N, 73.0826°W |
| Timezone | America/New_York |
| County | Greater Bridgeport Planning Region County |
| Nearest Airport | Hudson Valley Regional (POU) 46 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 39.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 91.8 / 100 |
| Social Vulnerability | 45.3 / 100 |
| Community Resilience | 59.9 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Relatively High |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Relatively High |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively High |
| Drought | Very Low |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
| Coastal Flood | Very High |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
18 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 | 132 km | 10 km |
| Jan 12, 2015 | 0 km NE of Wauregan, Connecticut | M3.3 | 109 km | 5 km |
| Jun 16, 2000 | 5 km NE of Granville, Massachusetts | M3.3 | 89 km | 10 km |
| Oct 2, 1994 | 1 km NW of Hardwick, Massachusetts | M3.3 | 135 km | 10 km |
| Apr 9, 2019 | 63 km SSE of Sagaponack, New York | M3.0 | 138 km | 7 km |
| Aug 3, 2025 | 0 km W of Little Ferry, New Jersey | M3.0 | 97 km | 10 km |
| Oct 28, 1991 | 3 km WNW of Stamford, Connecticut | M3.0 | 50 km | 10 km |
| Feb 3, 2009 | 1 km ESE of Victory Gardens, New Jersey | M3.0 | 131 km | 0 km |
| Aug 5, 2025 | 1 km N of Hillsdale, New Jersey | M2.8 | 87 km | 12 km |
| Mar 10, 1992 | 2 km SW of Napeague, New York | M2.8 | 91 km | 10 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 52 km | 9 km |
| Aug 14, 2014 | 6 km SW of Deep River Center, Connecticut | M2.7 | 49 km | 4 km |
| Jan 13, 2015 | 2 km E of Wauregan, Connecticut | M2.6 | 110 km | 9 km |
| May 1, 2024 | 1 km NW of Gladstone, New Jersey | M2.6 | 149 km | 5 km |
| Aug 22, 2000 | 2 km WSW of Brewster Hill, New York | M2.6 | 47 km | 7 km |
| Oct 27, 2001 | 1 km NNW of Manhattan, New York | M2.6 | 95 km | 5 km |
| Aug 14, 2015 | 3 km SE of Mendham, New Jersey | M2.6 | 141 km | 8 km |
| Jan 15, 1992 | 5 km NNE of Tuxedo Park, New York | M2.5 | 91 km | 7 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Hurricane History
4 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 | 278 km |
| 2014 | Arthur | Category 1 | 75 mph | 281 km |
| 1991 | Bob | Category 2 | 109 mph | 125 km |
| 1985 | Gloria | Category 1 | 86 mph | 68 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tornado History
220 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 19 fatalities, 958 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 10, 1989 | EF4 | 16 km | 3.0 mi | 0 |
| Oct 3, 1979 | EF4 | 71 km | 11.3 mi | 3 |
| Jun 1, 2011 | EF3 | 90 km | 37.6 mi | 3 |
| Jul 29, 1971 | EF3 | 25 km | 0.1 mi | 0 |
| May 24, 1962 | EF3 | 25 km | 11.6 mi | 1 |
| May 10, 1954 | EF3 | 83 km | 0.3 mi | 0 |
| Aug 21, 1951 | EF3 | 56 km | 0.1 mi | 0 |
| May 15, 2018 | EF2 | 54 km | 1.2 mi | 0 |
| Jul 12, 2006 | EF2 | 72 km | 10.1 mi | 0 |
| Jun 23, 2001 | EF2 | 53 km | 0.5 mi | 0 |
| May 18, 2000 | EF2 | 92 km | 0.2 mi | 0 |
| Aug 8, 1999 | EF2 | 59 km | 4.0 mi | 0 |
| Sep 7, 1998 | EF2 | 90 km | 0.2 mi | 0 |
| Jul 3, 1997 | EF2 | 95 km | 4.5 mi | 0 |
| Jul 3, 1997 | EF2 | 95 km | 3.7 mi | 0 |
| Jul 10, 1989 | EF2 | 31 km | 5.0 mi | 0 |
| Jul 10, 1989 | EF2 | 51 km | 0.5 mi | 0 |
| Jul 10, 1989 | EF2 | 62 km | 0.2 mi | 0 |
| Jul 10, 1989 | EF2 | 60 km | 10.0 mi | 0 |
| Jul 5, 1984 | EF2 | 40 km | 3.0 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 | — | 59 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
4 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (23,000 acres, 1985).
| Year | Name | Acres Burned | Distance |
| 1985 | UNNAMED | 23,000 | 88 km |
| 2012 | CRESCENT BOW FIRE | 1,068 | 53 km |
| 1988 | UNNAMED | 833 | 88 km |
| 2016 | SHERWOOD | 642 | 86 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 27°F (-3°C) | 3.8 in | Coldest |
| February | 31°F (-1°C) | 3.4 in | Driest |
| March | 39°F (4°C) | 4.2 in | |
| April | 49°F (9°C) | 4.3 in | Wettest |
| May | 59°F (15°C) | 4.3 in | |
| June | 68°F (20°C) | 3.8 in | |
| July | 73°F (23°C) | 3.7 in | Warmest |
| August | 72°F (22°C) | 3.8 in | |
| September | 64°F (18°C) | 3.8 in | |
| October | 53°F (12°C) | 3.8 in | |
| November | 44°F (7°C) | 4.3 in | |
| December | 34°F (1°C) | 4.1 in |
Derby has a seasonal temperature swing of 45°F / from 27°F in January to 73°F in July. Total annual precipitation is 47.0 inches, with April being the wettest month (4.3") and February the driest (3.4").