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Weather & Climate in Cornwall, ON
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Cornwall experiences four distinct seasons with an average annual temperature of 47°F (8°C). Winters average 19°F in January while summers reach 71°F in July. The area gets 265 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 47.6 inches (wetter than the 38-inch national average). The area receives 63.3 inches of snow annually, making winter weather a significant factor for residents. The city sits at an elevation of 197 feet.
Temperature
19°F Jan (-7°C)
71°F Jul (22°C)
| Annual Average | 46.8°F |
| 13% below US avg | |
| January Average | 19°F (-7°C) |
| July Average | 71°F (22°C) |
| Sunny Days | 265 days/yr |
Geography
| Elevation | 197 ft (60 m) |
| Area | 23.8 sq mi (61.5 km²) |
| Population Density | 2,015/sq mi |
| Coordinates | 45.0181°N, 74.7282°W |
| Timezone | America/Toronto |
Precipitation & Snow
Air Quality
Earthquake History
159 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M5.4.
| Jun 23, 2010 | 29 km NNE of Val-des-Monts, Canada | M5.4 | 113 km | 19 km |
| Apr 20, 2002 | 8 km NNW of Au Sable Forks, New York | M5.3 | 99 km | 5 km |
| Mar 14, 1996 | 7 km WNW of Saint-Adolphe-d'Howard, Canada | M4.5 | 111 km | 18 km |
| May 17, 1991 | 7 km WNW of Rigaud, Canada | M4.4 | 59 km | 18 km |
| Oct 31, 1999 | 7 km SW of Morin-Heights, Canada | M4.2 | 98 km | 18 km |
| May 24, 1997 | 6 km W of Saint-Adolphe-d'Howard, Canada | M4.2 | 109 km | 10 km |
| Apr 18, 1998 | 4 km N of Plantagenet, Canada | M4.1 | 65 km | 18 km |
| Aug 6, 2000 | 7 km SSW of La Minerve, Canada | M4.0 | 132 km | 18 km |
| Nov 17, 1992 | 16 km ENE of Saint-André-Avellin, Canada | M4.0 | 84 km | 18 km |
| Feb 25, 2006 | 4 km NE of Thurso, Canada | M4.0 | 77 km | 11 km |
| Oct 10, 2012 | 7 km ESE of Verchères, Canada | M3.9 | 140 km | 9 km |
| Jul 30, 1993 | 1 km NE of Salaberry-de-Valleyfield, Canada | M3.9 | 55 km | 8 km |
| Oct 7, 1990 | 21 km WNW of La Minerve, Canada | M3.9 | 149 km | 18 km |
| Mar 16, 2011 | 6 km ENE of Hawkesbury, Canada | M3.9 | 68 km | 10 km |
| Sep 18, 2011 | 1 km E of Thurso, Canada | M3.8 | 76 km | 5 km |
| Apr 20, 2000 | 7 km WSW of Newcomb, New York | M3.8 | 125 km | 5 km |
| Jul 30, 1998 | 0 km ENE of Lac-Simon, Canada | M3.8 | 127 km | 10 km |
| Sep 23, 1993 | 11 km SE of La Conception, Canada | M3.8 | 117 km | 18 km |
| Oct 6, 2000 | 1 km WSW of Ormstown, Canada | M3.8 | 57 km | 18 km |
| Nov 16, 1993 | 5 km SSE of Saint-Édouard, Canada | M3.8 | 99 km | 17 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tsunami History
1 tsunami recorded within 500 km. Highest wave on record: 15.0 m (49 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1908 | NOTRE DAME DE LA SALETTE | Meteorological | 15.0 m | 33 | 108 km |
Source: NOAA/NCEI Historical Tsunami Database.
Wildfire History
1 wildfire (100+ acres) recorded within 100 km. Largest: FLAT ROCK FIRE (658 acres, 2018).
| Year | Name | Acres Burned | Distance |
| 2018 | FLAT ROCK FIRE | 658 | 87 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 19°F (-7°C) | 2.9 in | |
| February | 16°F (-9°C) | 2.6 in | Coldest |
| March | 27°F (-3°C) | 2.4 in | Driest |
| April | 42°F (5°C) | 3.2 in | |
| May | 55°F (13°C) | 3.3 in | |
| June | 64°F (18°C) | 3.7 in | Wettest |
| July | 71°F (22°C) | 3.6 in | Warmest |
| August | 68°F (20°C) | 3.5 in | |
| September | 59°F (15°C) | 3.7 in | |
| October | 47°F (8°C) | 3.4 in | |
| November | 36°F (2°C) | 3.5 in | |
| December | 21°F (-6°C) | 3.0 in |
Cornwall has a seasonal temperature swing of 55°F / from 16°F in February to 71°F in July. Total annual precipitation is 38.8 inches, with June being the wettest month (3.7") and March the driest (2.4").