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Weather & Climate in Mendham, NJ
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mendham experiences four distinct seasons with an average annual temperature of 53°F (11°C). Winters average 30°F in January while summers reach 75°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 45.5 inches. Air quality is rated Good with a median AQI of 39. The city sits at an elevation of 519 feet.
Temperature
30°F Jan (-1°C)
75°F Jul (24°C)
| Annual Average | 52.5°F |
| 3% below US avg | |
| January Average | 30°F (-1°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 519 ft (158 m) |
| Area | 6.0 sq mi (15.5 km²) |
| Population Density | 839/sq mi |
| Coordinates | 40.7673°N, 74.5978°W |
| Timezone | America/New_York |
| County | Morris County County |
| Nearest Airport | Central Jersey Regional (JVI) 17 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 39.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 92.9 / 100 |
| Social Vulnerability | 10.6 / 100 |
| Community Resilience | 89.5 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Relatively Moderate |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Relatively High |
| Heat Wave | Relatively Moderate |
| Winter Weather | Very High |
| Lightning | Relatively High |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Relatively High |
| Landslide | Relatively Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
29 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.8.
| Apr 5, 2024 | 2024 Tewksbury, New Jersey Earthquake | M4.8 | 16 km | 3 km |
| Jan 16, 1994 | 2 km W of Sinking Spring, Pennsylvania | M4.6 | 131 km | 5 km |
| Jan 16, 1994 | 0 km E of Sinking Spring, Pennsylvania | M4.2 | 129 km | 5 km |
| Apr 5, 2024 | 7 km WSW of Gladstone, New Jersey | M3.7 | 15 km | 4 km |
| Jan 9, 1992 | 4 km WNW of Robertsville, New Jersey | M3.1 | 50 km | 8 km |
| Aug 26, 2003 | 4 km NNW of Milford, New Jersey | M3.1 | 46 km | 3 km |
| Oct 28, 1991 | 3 km WNW of Stamford, Connecticut | M3.0 | 92 km | 10 km |
| Aug 3, 2025 | 0 km W of Little Ferry, New Jersey | M3.0 | 47 km | 10 km |
| Feb 3, 2009 | 1 km ESE of Victory Gardens, New Jersey | M3.0 | 13 km | 0 km |
| Jan 16, 1994 | 0 km SSE of Sinking Spring, Pennsylvania | M2.9 | 129 km | 5 km |
| May 24, 2024 | 6 km E of Califon, New Jersey | M2.9 | 15 km | 7 km |
| Apr 27, 2024 | 7 km WSW of Gladstone, New Jersey | M2.9 | 15 km | 5 km |
| May 10, 1993 | 1 km NW of Whitfield, Pennsylvania | M2.8 | 129 km | 5 km |
| Aug 5, 2025 | 1 km N of Hillsdale, New Jersey | M2.8 | 55 km | 12 km |
| Jul 1, 2009 | 3 km ESE of Pennsville, New Jersey | M2.8 | 146 km | 5 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 90 km | 9 km |
| Jan 25, 2015 | 4 km ESE of Downingtown, Pennsylvania | M2.6 | 124 km | 2 km |
| Jul 5, 1996 | 2 km NW of Chester Heights, Pennsylvania | M2.6 | 122 km | 18 km |
| Apr 5, 2024 | 6 km ESE of Califon, New Jersey | M2.6 | 17 km | 6 km |
| May 1, 2024 | 1 km NW of Gladstone, New Jersey | M2.6 | 8 km | 5 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 |
| 2012 | Sandy | Category 1 | 92 mph | 299 km |
| 2011 | Irene | Category 1 | 75 mph | 299 km |
| 1991 | Bob | Category 2 | 109 mph | 209 km |
| 1985 | Gloria | Category 2 | 98 mph | 111 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tornado History
269 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 17 fatalities, 169 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 29, 2021 | EF3 | 79 km | 3.4 mi | 0 |
| May 31, 1998 | EF3 | 73 km | 20.0 mi | 0 |
| Jul 27, 1994 | EF3 | 98 km | 2.0 mi | 3 |
| Oct 18, 1990 | EF3 | 35 km | 0.5 mi | 0 |
| Jul 14, 1988 | EF3 | 63 km | 7.2 mi | 0 |
| Jul 26, 1981 | EF3 | 83 km | 3.3 mi | 0 |
| Sep 26, 1977 | EF3 | 45 km | 5.9 mi | 0 |
| Mar 21, 1976 | EF3 | 54 km | 0.5 mi | 0 |
| May 28, 1973 | EF3 | 14 km | 0.4 mi | 0 |
| May 28, 1973 | EF3 | 9 km | 0.4 mi | 0 |
| Jun 24, 1960 | EF3 | 57 km | 12.9 mi | 0 |
| Apr 1, 2023 | EF2 | 86 km | 0.1 mi | 0 |
| Apr 1, 2023 | EF2 | 74 km | 1.6 mi | 0 |
| Apr 1, 2023 | EF2 | 70 km | 2.1 mi | 0 |
| Feb 21, 2023 | EF2 | 55 km | 5.8 mi | 0 |
| Sep 1, 2021 | EF2 | 91 km | 8.3 mi | 1 |
| Jul 29, 2021 | EF2 | 56 km | 6.3 mi | 0 |
| Aug 4, 2020 | EF2 | 82 km | 20.8 mi | 0 |
| Jul 29, 2009 | EF2 | 58 km | 4.6 mi | 0 |
| Jul 29, 2009 | EF2 | 53 km | 7.4 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
3 tsunamis 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 | — | 126 km |
| 1895 | HIGH BRIDGE, NJ | Earthquake | — | — | 27 km |
| 1840 | PHILADELPHIA, PENNSYLVANIA | Earthquake | — | — | 119 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (23,000 acres, 1985).
| Year | Name | Acres Burned | Distance |
| 1985 | UNNAMED | 23,000 | 62 km |
| 2016 | 16 MILE | 7,896 | 67 km |
| 2024 | JENNINGS CREEK | 5,069 | 52 km |
| 1992 | UNNAMED | 4,470 | 86 km |
| 2023 | JIMMYS WATER HOLE | 3,585 | 87 km |
| 2002 | UNNAMED | 2,824 | 85 km |
| 2015 | ROOSA GAP | 2,747 | 98 km |
| 2010 | FORT DIX RANGE 1-14 | 2,615 | 84 km |
| 1997 | UNNAMED | 1,793 | 87 km |
| 2002 | JAKES BRANCH | 1,364 | 100 km |
| 1995 | UNNAMED | 1,318 | 85 km |
| 1998 | UNNAMED | 1,118 | 96 km |
| 1997 | UNNAMED | 1,042 | 99 km |
| 2002 | UNNAMED | 1,002 | 87 km |
| 2003 | UNNAMED | 974 | 93 km |
| 1992 | UNNAMED | 959 | 83 km |
| 1986 | LAKEHURST NAVAL AIR | 906 | 85 km |
| 1999 | UNNAMED | 892 | 93 km |
| 1995 | UNNAMED | 877 | 84 km |
| 1991 | UNNAMED | 860 | 86 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 30°F (-1°C) | 3.9 in | |
| February | 30°F (-1°C) | 3.2 in | Coldest, Driest |
| March | 38°F (3°C) | 4.1 in | |
| April | 48°F (9°C) | 4.3 in | |
| May | 59°F (15°C) | 4.8 in | |
| June | 67°F (19°C) | 4.3 in | |
| July | 75°F (24°C) | 5.0 in | Warmest, Wettest |
| August | 71°F (21°C) | 4.5 in | |
| September | 64°F (18°C) | 4.6 in | |
| October | 52°F (11°C) | 3.9 in | |
| November | 43°F (6°C) | 4.3 in | |
| December | 33°F (0°C) | 3.9 in |
Mendham has a seasonal temperature swing of 45°F / from 30°F in February to 75°F in July. Total annual precipitation is 50.8 inches, with July being the wettest month (5.0") and February the driest (3.2").