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Weather & Climate in Sarnia, ON
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Sarnia experiences four distinct seasons with an average annual temperature of 47°F (9°C). Winters average 23°F in January while summers reach 71°F in July. The area gets 274 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 33.9 inches. The area receives 8.9 inches of snow annually. The city sits at an elevation of 610 feet.
Temperature
23°F Jan (-5°C)
71°F Jul (22°C)
| Annual Average | 47.4°F |
| 12% below US avg | |
| January Average | 23°F (-5°C) |
| July Average | 71°F (22°C) |
| Sunny Days | 274 days/yr |
Geography
| Elevation | 610 ft (186 m) |
| Area | 4.9 sq mi (12.6 km²) |
| Population Density | 133/sq mi |
| Coordinates | 42.9787°N, 82.4041°W |
| Timezone | America/Toronto |
Precipitation & Snow
Air Quality
Earthquake History
9 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.4.
| Apr 20, 2018 | Michigan | M3.4 | 108 km | 3 km |
| Feb 23, 2011 | 18 km NE of Leamington, Canada | M3.0 | 91 km | 5 km |
| Apr 12, 2007 | 11 km NW of Put-in-Bay, Ohio | M2.8 | 146 km | 5 km |
| Sep 22, 1999 | 16 km NW of Mentor-on-the-Lake, Ohio | M2.8 | 149 km | 18 km |
| May 14, 2017 | 18 km ENE of Leamington, Canada | M2.6 | 94 km | 5 km |
| Sep 7, 2012 | 17 km ESE of Stony Point, Michigan | M2.5 | 136 km | 5 km |
| Mar 8, 2010 | 7 km ENE of Grosse Ile, Michigan | M2.5 | 106 km | 18 km |
| May 23, 2022 | 2 km NNW of Corunna, Canada | M2.5 | 9 km | 5 km |
| Feb 17, 2013 | 31 km E of Leamington, Canada | M2.5 | 108 km | 5 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tsunami History
2 tsunamis recorded within 500 km. Highest wave on record: 2.7 m (9 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1823 | LAKE ERIE | Unknown | 2.7 m | — | 138 km |
| 1952 | LAKE HURON, MI | Avalanche | 1.5 m | — | 14 km |
Source: NOAA/NCEI Historical Tsunami Database.
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 23°F (-5°C) | 2.1 in | Coldest |
| February | 24°F (-5°C) | 2.0 in | Driest |
| March | 33°F (1°C) | 2.3 in | |
| April | 44°F (7°C) | 2.9 in | |
| May | 56°F (13°C) | 3.0 in | |
| June | 66°F (19°C) | 3.3 in | |
| July | 71°F (22°C) | 2.8 in | Warmest |
| August | 70°F (21°C) | 3.1 in | |
| September | 63°F (17°C) | 3.9 in | Wettest |
| October | 52°F (11°C) | 2.8 in | |
| November | 40°F (4°C) | 3.2 in | |
| December | 29°F (-2°C) | 2.6 in |
Sarnia has a seasonal temperature swing of 48°F / from 23°F in January to 71°F in July. Total annual precipitation is 33.9 inches, with September being the wettest month (3.9") and February the driest (2.0").