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Weather & Climate in Portsmouth, NH
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Portsmouth experiences four distinct seasons with an average annual temperature of 48°F (9°C). Winters average 24°F in January while summers reach 70°F in July. The area gets 259 sunny days per year, above the national average. Annual precipitation totals 50.7 inches (wetter than the 38-inch national average). The area receives 65.0 inches of snow annually, making winter weather a significant factor for residents. Air quality is rated Good with a median AQI of 37. The city sits at an elevation of 51 feet.
Temperature
24°F Jan (-4°C)
70°F Jul (21°C)
| Annual Average | 47.6°F |
| 12% below US avg | |
| January Average | 24°F (-4°C) |
| July Average | 70°F (21°C) |
| Sunny Days | 259 days/yr |
Geography
| Elevation | 51 ft (16 m) |
| Area | 15.7 sq mi (40.6 km²) |
| Population Density | 1,426/sq mi |
| Coordinates | 43.0606°N, 70.7803°W |
| Timezone | America/New_York |
| County | York County County |
| Nearest Airport | Portsmouth International At Pease (PSM) 2 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 37.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 81.5 / 100 |
| Social Vulnerability | 16.3 / 100 |
| Community Resilience | 84.8 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Relatively Moderate |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Very Low |
| Strong Wind | Relatively Low |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Moderate |
| Lightning | Relatively Moderate |
| Ice Storm | Very High |
| Drought | Relatively Moderate |
| Cold Wave | Relatively Low |
| Landslide | Relatively Low |
| Coastal Flood | Relatively High |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
41 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.7.
| Oct 16, 2012 | 5 km W of Hollis Center, Maine | M4.7 | 61 km | 16 km |
| Aug 21, 1996 | 12 km N of Livermore, New Hampshire | M3.8 | 133 km | 10 km |
| Jan 27, 2025 | 9 km SE of York Harbor, Maine | M3.8 | 17 km | 11 km |
| Oct 2, 1994 | 6 km W of Hardwick, Massachusetts | M3.7 | 146 km | 10 km |
| Jan 3, 2000 | 4 km W of Leeds, Maine | M3.5 | 147 km | 10 km |
| Oct 6, 1992 | 1 km SW of Canterbury, New Hampshire | M3.4 | 71 km | 5 km |
| Oct 2, 1994 | 1 km NW of Hardwick, Massachusetts | M3.3 | 141 km | 10 km |
| Sep 26, 2010 | 2 km SW of Canterbury, New Hampshire | M3.2 | 72 km | 5 km |
| Jan 10, 1999 | 2 km ENE of Merrimac, Massachusetts | M3.1 | 29 km | 2 km |
| Jan 10, 1999 | 1 km NNE of Merrimac, Massachusetts | M3.0 | 30 km | 2 km |
| Nov 20, 1994 | 4 km WNW of Norway, Maine | M3.0 | 131 km | 5 km |
| Jan 27, 2000 | 3 km WNW of Fremont, New Hampshire | M3.0 | 33 km | 1 km |
| Jul 22, 2003 | 72 km NNE of Provincetown, Massachusetts | M3.0 | 99 km | 10 km |
| Apr 25, 2023 | 4 km SW of Center Sandwich, New Hampshire | M2.9 | 98 km | 8 km |
| Jun 7, 2010 | 29 km SE of York Beach, Maine | M2.9 | 39 km | 10 km |
| Jan 8, 1998 | 52 km ENE of Rockport, Massachusetts | M2.9 | 64 km | 25 km |
| Sep 28, 2002 | 2 km N of Wilton, New Hampshire | M2.8 | 80 km | 5 km |
| Jul 28, 2024 | 6 km W of Gardiner, Maine | M2.8 | 150 km | 8 km |
| Mar 21, 2016 | 4 km ESE of Warner, New Hampshire | M2.8 | 83 km | 7 km |
| Mar 23, 1992 | 5 km SE of Hill, New Hampshire | M2.8 | 85 km | 5 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 | 56 km |
| 1985 | Gloria | Category 1 | 86 mph | 210 km |
Source: NOAA IBTrACS (Category 1+, 1980–2026).
Tornado History
114 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 2 fatalities, 64 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Sep 29, 1974 | EF3 | 63 km | 0.1 mi | 0 |
| Jun 9, 1953 | EF3 | 18 km | 1.5 mi | 0 |
| Jul 28, 2014 | EF2 | 76 km | 1.9 mi | 0 |
| Jul 24, 2008 | EF2 | 44 km | 50.5 mi | 1 |
| May 21, 2006 | EF2 | 17 km | 0.1 mi | 0 |
| Jul 6, 1999 | EF2 | 52 km | 7.5 mi | 0 |
| May 31, 1998 | EF2 | 95 km | 0.5 mi | 0 |
| Jul 3, 1997 | EF2 | 88 km | 2.0 mi | 0 |
| Jun 22, 1981 | EF2 | 52 km | 8.7 mi | 0 |
| May 3, 1976 | EF2 | 10 km | 1.0 mi | 0 |
| Jul 21, 1972 | EF2 | 67 km | 7.6 mi | 0 |
| Jul 3, 1972 | EF2 | 66 km | 1.0 mi | 0 |
| Jul 17, 1968 | EF2 | 87 km | 0.1 mi | 0 |
| Oct 10, 1966 | EF2 | 41 km | 0.2 mi | 0 |
| Aug 28, 1965 | EF2 | 60 km | 2.0 mi | 0 |
| Jul 18, 1963 | EF2 | 69 km | 0.1 mi | 0 |
| Jun 9, 1963 | EF2 | 59 km | 10.0 mi | 0 |
| May 20, 1963 | EF2 | 99 km | 0.3 mi | 0 |
| May 14, 1963 | EF2 | 32 km | 8.7 mi | 0 |
| Jul 2, 1961 | EF2 | 75 km | 2.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
1 tsunami recorded within 500 km. Highest wave on record: 3.6 m (12 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 2008 | MAINE | Avalanche | 3.6 m | — | 120 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: THE RANGE (760 acres, 2005).
| Year | Name | Acres Burned | Distance |
| 2005 | THE RANGE | 760 | 95 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 24°F (-4°C) | 3.5 in | Coldest |
| February | 27°F (-3°C) | 3.2 in | Driest |
| March | 35°F (2°C) | 3.6 in | |
| April | 45°F (7°C) | 4.1 in | |
| May | 56°F (13°C) | 3.5 in | |
| June | 65°F (18°C) | 3.4 in | |
| July | 70°F (21°C) | 3.2 in | Warmest |
| August | 69°F (20°C) | 3.3 in | |
| September | 61°F (16°C) | 3.4 in | |
| October | 50°F (10°C) | 4.1 in | |
| November | 41°F (5°C) | 4.5 in | Wettest |
| December | 30°F (-1°C) | 3.8 in |
Portsmouth has a seasonal temperature swing of 46°F / from 24°F in January to 70°F in July. Total annual precipitation is 43.4 inches, with November being the wettest month (4.5") and February the driest (3.2").