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Weather & Climate in St. Marys, OH
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
St. Marys experiences four distinct seasons with an average annual temperature of 51°F (11°C). Winters average 26°F in January while summers reach 73°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 41.2 inches. The area receives 18.5 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 873 feet.
Temperature
26°F Jan (-3°C)
73°F Jul (23°C)
| Annual Average | 51.0°F |
| 6% below US avg | |
| January Average | 26°F (-3°C) |
| July Average | 73°F (23°C) |
| Sunny Days | 275 days/yr |
Geography
| Elevation | 873 ft (266 m) |
| Area | 4.6 sq mi (12.0 km²) |
| Population Density | 1,781/sq mi |
| Coordinates | 40.5476°N, 84.3923°W |
| Timezone | America/New_York |
| County | Auglaize County County |
| Nearest Airport | James M Cox Dayton International (DAY) 46 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 43.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very Low |
| Risk Score | 41.8 / 100 |
| Social Vulnerability | 25.1 / 100 |
| Community Resilience | 95.4 / 100 |
Hazard Breakdown
| Tornado | Relatively Low |
| Hurricane | Very Low |
| Earthquake | Relatively Low |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Relatively Low |
| Strong Wind | Relatively Low |
| Heat Wave | Very Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Low |
| Ice Storm | Relatively Low |
| Drought | No Rating |
| Cold Wave | Relatively Low |
| Landslide | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
10 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.0.
| Jan 26, 2012 | 5 km NE of Topeka, Indiana | M3.0 | 147 km | 5 km |
| Apr 17, 1990 | 8 km NW of Fort Recovery, Ohio | M3.0 | 40 km | 5 km |
| Apr 4, 1994 | 2 km WNW of Minster, Ohio | M2.9 | 16 km | 5 km |
| May 12, 2006 | 2 km E of Lima, Ohio | M2.8 | 34 km | 5 km |
| May 14, 2010 | 1 km ENE of Gibsonburg, Ohio | M2.7 | 131 km | 5 km |
| Jun 12, 2015 | 6 km NW of Convoy, Ohio | M2.6 | 55 km | 5 km |
| May 20, 2023 | 3 km SSE of Walbridge, Ohio | M2.6 | 135 km | 6 km |
| Jan 30, 2004 | 2 km S of Rockford, Ohio | M2.5 | 26 km | 5 km |
| Jun 4, 1990 | 4 km SSE of Van Buren, Ohio | M2.5 | 88 km | 5 km |
| Mar 18, 2024 | 4 km WSW of Millbury, Ohio | M2.5 | 136 km | 6 km |
Source: USGS Earthquake Catalog (M2.5+, 1990-2025). Sorted by magnitude.
Tornado History
492 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 54 fatalities, 1,279 injuries.
| Date | Rating | Distance | Path | Fatalities |
| May 27, 2019 | EF4 | 81 km | 18.2 mi | 0 |
| Nov 10, 2002 | EF4 | 41 km | 52.8 mi | 4 |
| Feb 18, 1992 | EF4 | 25 km | 2.8 mi | 0 |
| Apr 3, 1974 | EF4 | 93 km | 18.0 mi | 1 |
| Apr 11, 1965 | EF4 | 32 km | 32.5 mi | 13 |
| Apr 11, 1965 | EF4 | 22 km | 18.4 mi | 3 |
| Apr 11, 1965 | EF4 | 83 km | 52.5 mi | 4 |
| Mar 6, 1956 | EF4 | 100 km | 1.9 mi | 1 |
| Jun 8, 1953 | EF4 | 86 km | 118.0 mi | 17 |
| Mar 14, 2024 | EF3 | 74 km | 41.3 mi | 1 |
| Mar 14, 2024 | EF3 | 19 km | 31.3 mi | 3 |
| May 27, 2019 | EF3 | 25 km | 10.8 mi | 1 |
| May 27, 2019 | EF3 | 64 km | 10.5 mi | 0 |
| May 27, 2019 | EF3 | 85 km | 12.8 mi | 0 |
| May 27, 2019 | EF3 | 90 km | 9.9 mi | 0 |
| Aug 24, 2016 | EF3 | 80 km | 5.2 mi | 0 |
| Nov 10, 2002 | EF3 | 75 km | 9.0 mi | 0 |
| Nov 10, 2002 | EF3 | 47 km | 5.0 mi | 0 |
| Oct 24, 2001 | EF3 | 34 km | 32.0 mi | 0 |
| Nov 22, 1992 | EF3 | 91 km | 20.0 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950-2024, US only).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 26°F (-3°C) | 1.9 in | Coldest |
| February | 28°F (-2°C) | 1.8 in | Driest |
| March | 38°F (3°C) | 3.0 in | |
| April | 49°F (9°C) | 3.5 in | |
| May | 60°F (16°C) | 3.7 in | Wettest |
| June | 69°F (21°C) | 3.6 in | |
| July | 73°F (23°C) | 3.6 in | Warmest |
| August | 71°F (22°C) | 3.2 in | |
| September | 65°F (18°C) | 2.9 in | |
| October | 53°F (12°C) | 2.2 in | |
| November | 41°F (5°C) | 2.9 in | |
| December | 30°F (-1°C) | 2.6 in |
St. Marys has a seasonal temperature swing of 47°F / from 26°F in January to 73°F in July. Total annual precipitation is 34.7 inches, with May being the wettest month (3.7") and February the driest (1.8").