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Weather & Climate in Mount Hermon, NJ
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mount Hermon experiences four distinct seasons with an average annual temperature of 52°F (11°C). Winters average 29°F in January while summers reach 75°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 50.9 inches (wetter than the 38-inch national average). The area receives 27.1 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 39. The city sits at an elevation of 497 feet.
Temperature
29°F Jan (-2°C)
75°F Jul (24°C)
| Annual Average | 52.1°F |
| 4% below US avg | |
| January Average | 29°F (-2°C) |
| July Average | 75°F (24°C) |
| Sunny Days | 271 days/yr |
Geography
| Elevation | 497 ft (151 m) |
| Area | 0.5 sq mi (1.2 km²) |
| Population Density | 255/sq mi |
| Coordinates | 40.9219°N, 74.9940°W |
| Timezone | America/New_York |
| County | Morris County County |
| Nearest Airport | Pocono Mountains Regional (MPO) 25 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
32 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.8.
| Apr 5, 2024 | 2024 Tewksbury, New Jersey Earthquake | M4.8 | 32 km | 3 km |
| Jan 16, 1994 | 2 km W of Sinking Spring, Pennsylvania | M4.6 | 110 km | 5 km |
| Jan 16, 1994 | 0 km E of Sinking Spring, Pennsylvania | M4.2 | 108 km | 5 km |
| Apr 5, 2024 | 7 km WSW of Gladstone, New Jersey | M3.7 | 33 km | 4 km |
| Jan 9, 1992 | 4 km WNW of Robertsville, New Jersey | M3.1 | 83 km | 8 km |
| Aug 26, 2003 | 4 km NNW of Milford, New Jersey | M3.1 | 36 km | 3 km |
| Nov 14, 1997 | 0 km S of Rothsville, Pennsylvania | M3.0 | 137 km | 5 km |
| Oct 28, 1991 | 3 km WNW of Stamford, Connecticut | M3.0 | 120 km | 10 km |
| Aug 3, 2025 | 0 km W of Little Ferry, New Jersey | M3.0 | 80 km | 10 km |
| Feb 3, 2009 | 1 km ESE of Victory Gardens, New Jersey | M3.0 | 40 km | 0 km |
| Apr 27, 2024 | 7 km WSW of Gladstone, New Jersey | M2.9 | 33 km | 5 km |
| May 24, 2024 | 6 km E of Califon, New Jersey | M2.9 | 31 km | 7 km |
| Jan 16, 1994 | 0 km SSE of Sinking Spring, Pennsylvania | M2.9 | 109 km | 5 km |
| Aug 5, 2025 | 1 km N of Hillsdale, New Jersey | M2.8 | 81 km | 12 km |
| May 10, 1993 | 1 km NW of Whitfield, Pennsylvania | M2.8 | 108 km | 5 km |
| Jul 1, 2009 | 3 km ESE of Pennsville, New Jersey | M2.8 | 148 km | 5 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 115 km | 9 km |
| Mar 11, 1995 | 0 km ENE of Landisville, Pennsylvania | M2.7 | 150 km | 5 km |
| Jan 25, 2015 | 4 km ESE of Downingtown, Pennsylvania | M2.6 | 117 km | 2 km |
| Jul 5, 1996 | 2 km NW of Chester Heights, Pennsylvania | M2.6 | 121 km | 18 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 | 109 mph | 246 km |
| 1985 | Gloria | Category 2 | 98 mph | 147 km |
Source: NOAA IBTrACS (Category 1+, 1980-2026).
Tornado History
287 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 14 fatalities, 195 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 29, 2021 | EF3 | 88 km | 3.4 mi | 0 |
| May 31, 1998 | EF3 | 43 km | 20.0 mi | 0 |
| May 31, 1998 | EF3 | 91 km | 8.3 mi | 0 |
| Jul 27, 1994 | EF3 | 89 km | 2.0 mi | 3 |
| Oct 18, 1990 | EF3 | 53 km | 0.5 mi | 0 |
| Jul 14, 1988 | EF3 | 60 km | 7.2 mi | 0 |
| Jul 26, 1981 | EF3 | 52 km | 3.3 mi | 0 |
| Sep 26, 1977 | EF3 | 73 km | 5.9 mi | 0 |
| Mar 21, 1976 | EF3 | 17 km | 0.5 mi | 0 |
| May 28, 1973 | EF3 | 44 km | 0.4 mi | 0 |
| May 28, 1973 | EF3 | 24 km | 0.4 mi | 0 |
| Jun 24, 1960 | EF3 | 75 km | 12.9 mi | 0 |
| Apr 22, 2023 | EF2 | 98 km | 10.0 mi | 0 |
| Apr 1, 2023 | EF2 | 99 km | 2.1 mi | 0 |
| Feb 21, 2023 | EF2 | 76 km | 5.8 mi | 0 |
| Sep 1, 2021 | EF2 | 93 km | 8.3 mi | 1 |
| Jul 29, 2021 | EF2 | 64 km | 6.3 mi | 0 |
| Aug 4, 2020 | EF2 | 94 km | 20.8 mi | 0 |
| Jun 13, 2018 | EF2 | 80 km | 2.9 mi | 0 |
| Feb 25, 2017 | EF2 | 74 km | 12.5 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Tsunami History
2 tsunamis recorded within 500 km.
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1895 | HIGH BRIDGE, NJ | Earthquake | - | - | 30 km |
| 1840 | PHILADELPHIA, PENNSYLVANIA | Earthquake | - | - | 126 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
14 wildfires (100+ acres) recorded within 100 km. Largest: UNNAMED (23,000 acres, 1985).
| Year | Name | Acres Burned | Distance |
| 1985 | UNNAMED | 23,000 | 80 km |
| 2016 | 16 MILE | 7,896 | 33 km |
| 2024 | JENNINGS CREEK | 5,069 | 65 km |
| 2015 | ROOSA GAP | 2,747 | 93 km |
| 2009 | PENOBSCOT | 2,091 | 79 km |
| 2004 | CRYSTAL LAKE | 1,838 | 75 km |
| 1988 | UNNAMED | 833 | 81 km |
| 2020 | SEVEN PINES | 790 | 39 km |
| 1985 | UNNAMED | 737 | 79 km |
| 2015 | RAZOR FIRE | 728 | 60 km |
| 2015 | PIPELINE 1 | 666 | 62 km |
| 2016 | BEAR TOWN | 649 | 35 km |
| 2016 | SHERWOOD | 642 | 81 km |
| 1999 | WORTHINGTO | 514 | 12 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 29°F (-2°C) | 3.5 in | |
| February | 28°F (-2°C) | 3.0 in | Coldest, Driest |
| March | 37°F (3°C) | 3.7 in | |
| April | 47°F (9°C) | 4.1 in | |
| May | 58°F (14°C) | 4.5 in | |
| June | 66°F (19°C) | 4.3 in | |
| July | 75°F (24°C) | 4.6 in | Warmest, Wettest |
| August | 70°F (21°C) | 4.4 in | |
| September | 63°F (17°C) | 4.3 in | |
| October | 51°F (11°C) | 3.7 in | |
| November | 42°F (5°C) | 4.1 in | |
| December | 31°F (-0°C) | 3.6 in |
Mount Hermon has a seasonal temperature swing of 47°F / from 28°F in February to 75°F in July. Total annual precipitation is 47.6 inches, with July being the wettest month (4.6") and February the driest (3.0").