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Weather & Climate in Mercersburg, PA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Mercersburg experiences four distinct seasons with an average annual temperature of 55°F (13°C). Winters average 33°F in January while summers reach 78°F in July. The area gets 302 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 35.6 inches. Air quality is rated Good with a median AQI of 40. The city sits at an elevation of 547 feet.
Temperature
33°F Jan (0°C)
78°F Jul (25°C)
| Annual Average | 55.4°F |
| 3% above US avg | |
| January Average | 33°F (0°C) |
| July Average | 78°F (25°C) |
| Sunny Days | 302 days/yr |
Geography
| Elevation | 547 ft (167 m) |
| Area | 0.4 sq mi (0.9 km²) |
| Population Density | 2,156/sq mi |
| Coordinates | 39.8319°N, 77.9029°W |
| Timezone | America/New_York |
| County | Franklin County County |
| Nearest Airport | Hagerstown Regional/Richard A Henson Field (HGR) 13 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 40.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 76.4 / 100 |
| Social Vulnerability | 32.4 / 100 |
| Community Resilience | 63.5 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Relatively Moderate |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Relatively Low |
| Strong Wind | Relatively Moderate |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Moderate |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively Low |
| Drought | Relatively Moderate |
| Cold Wave | Very Low |
| Landslide | Relatively Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
16 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.6.
| Jul 16, 2010 | 5 km NNW of Barnesville, Maryland | M3.6 | 76 km | 7 km |
| Jun 13, 2019 | 9 km N of Blain, Pennsylvania | M3.4 | 74 km | 27 km |
| Jun 3, 2010 | 4 km ENE of Franklintown, Pennsylvania | M3.1 | 84 km | 2 km |
| Jan 17, 2016 | 3 km NE of Ranson, West Virginia | M3.0 | 57 km | 5 km |
| Nov 14, 1997 | 0 km S of Rothsville, Pennsylvania | M3.0 | 145 km | 5 km |
| Apr 24, 2009 | 1 km S of Franklintown, Pennsylvania | M2.9 | 79 km | 1 km |
| Sep 15, 2019 | 5 km ESE of East Berlin, Pennsylvania | M2.8 | 85 km | 5 km |
| Oct 25, 2009 | 4 km ENE of Franklintown, Pennsylvania | M2.8 | 84 km | 1 km |
| Mar 15, 1993 | 5 km W of Columbia, Maryland | M2.7 | 109 km | 5 km |
| Oct 28, 1994 | 1 km E of Mount Vernon, Maryland | M2.7 | 126 km | - |
| Mar 11, 1995 | 0 km ENE of Landisville, Pennsylvania | M2.7 | 132 km | 5 km |
| Jan 13, 1990 | 6 km ENE of Eldersburg, Maryland | M2.6 | 99 km | 5 km |
| Jun 25, 2021 | 2 km SE of Woodlawn, Maryland | M2.6 | 118 km | 3 km |
| Jan 18, 1994 | 3 km SE of Clay, Pennsylvania | M2.6 | 148 km | 5 km |
| Sep 29, 1997 | Virginia | M2.5 | 120 km | 3 km |
| Mar 10, 1993 | 3 km WSW of Columbia, Maryland | M2.5 | 110 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Tornado History
299 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 52 injuries.
| Date | Rating | Distance | Path | Fatalities |
| Jul 19, 1996 | EF3 | 87 km | 2.2 mi | 0 |
| May 22, 1983 | EF3 | 58 km | 2.0 mi | 0 |
| Jun 7, 1980 | EF3 | 76 km | 1.5 mi | 0 |
| Apr 16, 1961 | EF3 | 41 km | 0.1 mi | 0 |
| Apr 5, 1952 | EF3 | 79 km | 17.5 mi | 0 |
| Apr 19, 2019 | EF2 | 82 km | 4.9 mi | 0 |
| Apr 19, 2019 | EF2 | 9 km | 2.9 mi | 0 |
| Nov 2, 2018 | EF2 | 83 km | 5.5 mi | 0 |
| Apr 28, 2011 | EF2 | 89 km | 2.6 mi | 0 |
| Sep 17, 2004 | EF2 | 57 km | 3.0 mi | 0 |
| Sep 17, 2004 | EF2 | 53 km | 2.0 mi | 0 |
| Sep 17, 2004 | EF2 | 77 km | 5.0 mi | 0 |
| Sep 24, 2001 | EF2 | 80 km | 5.0 mi | 0 |
| Jul 19, 1996 | EF2 | 53 km | 2.0 mi | 0 |
| Apr 30, 1994 | EF2 | 22 km | 6.0 mi | 0 |
| Oct 9, 1992 | EF2 | 87 km | 2.0 mi | 0 |
| Sep 18, 1991 | EF2 | 94 km | 4.0 mi | 0 |
| Jun 8, 1990 | EF2 | 86 km | 1.0 mi | 0 |
| Nov 20, 1989 | EF2 | 88 km | 3.5 mi | 0 |
| Nov 16, 1989 | EF2 | 66 km | 9.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Wildfire History
2 wildfires (100+ acres) recorded within 100 km. Largest: BEAR DEN (945 acres, 2014).
| Year | Name | Acres Burned | Distance |
| 2014 | BEAR DEN | 945 | 66 km |
| 2005 | UNNAMED | 510 | 75 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 33°F (0°C) | 2.6 in | |
| February | 32°F (0°C) | 2.5 in | Coldest, Driest |
| March | 41°F (5°C) | 3.2 in | |
| April | 51°F (11°C) | 3.4 in | |
| May | 61°F (16°C) | 3.9 in | Wettest |
| June | 69°F (21°C) | 3.7 in | |
| July | 78°F (25°C) | 3.6 in | Warmest |
| August | 72°F (22°C) | 3.3 in | |
| September | 65°F (19°C) | 3.2 in | |
| October | 54°F (12°C) | 3.3 in | |
| November | 44°F (7°C) | 3.3 in | |
| December | 34°F (1°C) | 2.8 in |
Mercersburg has a seasonal temperature swing of 45°F / from 32°F in February to 78°F in July. Total annual precipitation is 38.8 inches, with May being the wettest month (3.9") and February the driest (2.5").