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Weather & Climate in Mountainside, NJ
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mountainside experiences four distinct seasons with an average annual temperature of 55°F (13°C). Winters average 33°F in January while summers reach 77°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 50.4 inches (wetter than the 38-inch national average). The area receives 26.3 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 231 feet.
Temperature
33°F Jan (0°C)
77°F Jul (25°C)
| Annual Average | 54.6°F |
| 1% above US avg | |
| January Average | 33°F (0°C) |
| July Average | 77°F (25°C) |
| Sunny Days | 271 days/yr |
Geography
| Elevation | 231 ft (70 m) |
| Area | 4.1 sq mi (10.5 km²) |
| Population Density | 1,742/sq mi |
| Coordinates | 40.6807°N, 74.3603°W |
| Timezone | America/New_York |
| County | Union County County |
| Nearest Airport | Newark Liberty International (EWR) 10 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 39.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively High |
| Risk Score | 95.5 / 100 |
| Social Vulnerability | 55.8 / 100 |
| Community Resilience | 30.3 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Hurricane | Relatively Moderate |
| Earthquake | Relatively Moderate |
| Wildfire | Very Low |
| Flood | Relatively High |
| Hail | Very Low |
| Strong Wind | Very High |
| Heat Wave | Relatively Moderate |
| Winter Weather | Very High |
| Lightning | Very High |
| Ice Storm | Very High |
| Drought | Very Low |
| Cold Wave | Relatively Moderate |
| Landslide | Very Low |
| Coastal Flood | Relatively Moderate |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
28 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.8.
| Apr 5, 2024 | 2024 Tewksbury, New Jersey Earthquake | M4.8 | 34 km | 3 km |
| Jan 16, 1994 | 2 km W of Sinking Spring, Pennsylvania | M4.6 | 147 km | 5 km |
| Jan 16, 1994 | 0 km E of Sinking Spring, Pennsylvania | M4.2 | 145 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 | 35 km | 8 km |
| Aug 26, 2003 | 4 km NNW of Milford, New Jersey | M3.1 | 63 km | 3 km |
| Aug 3, 2025 | 0 km W of Little Ferry, New Jersey | M3.0 | 32 km | 10 km |
| Oct 28, 1991 | 3 km WNW of Stamford, Connecticut | M3.0 | 79 km | 10 km |
| Feb 3, 2009 | 1 km ESE of Victory Gardens, New Jersey | M3.0 | 25 km | 0 km |
| Jan 16, 1994 | 0 km SSE of Sinking Spring, Pennsylvania | M2.9 | 145 km | 5 km |
| May 24, 2024 | 6 km E of Califon, New Jersey | M2.9 | 34 km | 7 km |
| Apr 27, 2024 | 7 km WSW of Gladstone, New Jersey | M2.9 | 33 km | 5 km |
| Aug 5, 2025 | 1 km N of Hillsdale, New Jersey | M2.8 | 46 km | 12 km |
| May 10, 1993 | 1 km NW of Whitfield, Pennsylvania | M2.8 | 145 km | 5 km |
| Jul 1, 2009 | 3 km ESE of Pennsville, New Jersey | M2.8 | 150 km | 5 km |
| Apr 12, 1991 | 2 km ENE of North Castle, New York | M2.7 | 79 km | 9 km |
| Jan 25, 2015 | 4 km ESE of Downingtown, Pennsylvania | M2.6 | 134 km | 2 km |
| Jul 5, 1996 | 2 km NW of Chester Heights, Pennsylvania | M2.6 | 129 km | 18 km |
| Apr 5, 2024 | 6 km ESE of Califon, New Jersey | M2.6 | 34 km | 6 km |
| Apr 10, 2024 | 5 km WSW of Gladstone, New Jersey | M2.6 | 30 km | 9 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 | 283 km |
| 2011 | Irene | Category 1 | 75 mph | 292 km |
| 1991 | Bob | Category 2 | 109 mph | 188 km |
| 1985 | Gloria | Category 2 | 98 mph | 90 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tornado History
247 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 14 fatalities, 136 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 29, 2021 | EF3 | 82 km | 3.4 mi | 0 |
| May 31, 1998 | EF3 | 93 km | 20.0 mi | 0 |
| Oct 18, 1990 | EF3 | 41 km | 0.5 mi | 0 |
| Jul 14, 1988 | EF3 | 74 km | 7.2 mi | 0 |
| Sep 26, 1977 | EF3 | 37 km | 5.9 mi | 0 |
| Mar 21, 1976 | EF3 | 77 km | 0.5 mi | 0 |
| May 28, 1973 | EF3 | 18 km | 0.4 mi | 0 |
| May 28, 1973 | EF3 | 36 km | 0.4 mi | 0 |
| Jun 24, 1960 | EF3 | 57 km | 12.9 mi | 0 |
| Apr 1, 2023 | EF2 | 59 km | 1.6 mi | 0 |
| Apr 1, 2023 | EF2 | 59 km | 2.1 mi | 0 |
| Apr 1, 2023 | EF2 | 68 km | 0.1 mi | 0 |
| Feb 21, 2023 | EF2 | 53 km | 5.8 mi | 0 |
| Sep 1, 2021 | EF2 | 98 km | 8.3 mi | 1 |
| Jul 29, 2021 | EF2 | 62 km | 6.3 mi | 0 |
| Aug 4, 2020 | EF2 | 84 km | 20.8 mi | 0 |
| Jul 29, 2009 | EF2 | 68 km | 7.4 mi | 0 |
| Jul 29, 2009 | EF2 | 80 km | 4.6 mi | 0 |
| Aug 8, 2007 | EF2 | 22 km | 5.9 mi | 0 |
| Jul 12, 2006 | EF2 | 60 km | 10.1 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 | — | 107 km |
| 1895 | HIGH BRIDGE, NJ | Earthquake | — | — | 44 km |
| 1840 | PHILADELPHIA, PENNSYLVANIA | Earthquake | — | — | 121 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 | 61 km |
| 1995 | GREENWOOD STATE FOREST | 21,271 | 94 km |
| 2019 | SPRING HILL FIRE | 8,182 | 99 km |
| 2016 | 16 MILE | 7,896 | 88 km |
| 1992 | FORKED RIVER MOUTAIN APR | 5,093 | 91 km |
| 2024 | JENNINGS CREEK | 5,069 | 56 km |
| 1992 | POWER PLANT | 4,928 | 95 km |
| 1992 | UNNAMED | 4,470 | 77 km |
| 2023 | JIMMYS WATER HOLE | 3,585 | 75 km |
| 2002 | UNNAMED | 2,824 | 76 km |
| 1992 | FOUR MILE COLONY | 2,647 | 93 km |
| 2010 | FORT DIX RANGE 1-14 | 2,615 | 76 km |
| 1997 | UNNAMED | 1,793 | 77 km |
| 2002 | JAKES BRANCH | 1,364 | 86 km |
| 1995 | UNNAMED | 1,318 | 75 km |
| 1991 | UNNAMED | 1,280 | 93 km |
| 1998 | UNNAMED | 1,118 | 88 km |
| 1997 | UNNAMED | 1,042 | 89 km |
| 2015 | WOODMANSIE FIRE | 1,003 | 90 km |
| 2002 | UNNAMED | 1,002 | 77 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 33°F (0°C) | 3.9 in | |
| February | 31°F (-1°C) | 3.1 in | Coldest, Driest |
| March | 40°F (4°C) | 4.1 in | |
| April | 50°F (10°C) | 4.3 in | |
| May | 60°F (16°C) | 4.7 in | |
| June | 69°F (20°C) | 4.2 in | |
| July | 77°F (25°C) | 5.0 in | Warmest, Wettest |
| August | 72°F (22°C) | 4.4 in | |
| September | 65°F (18°C) | 4.6 in | |
| October | 53°F (12°C) | 3.9 in | |
| November | 44°F (7°C) | 4.3 in | |
| December | 34°F (1°C) | 3.8 in |
Mountainside has a seasonal temperature swing of 46°F / from 31°F in February to 77°F in July. Total annual precipitation is 50.4 inches, with July being the wettest month (5.0") and February the driest (3.1").