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Weather & Climate in Sumas, WA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Sumas experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 38°F in January while summers reach 64°F in July. The area gets 233 sunny days per year, above the national average. Annual precipitation totals 49.9 inches (wetter than the 38-inch national average). The area receives 10.8 inches of snow annually. Air quality is rated Good with a median AQI of 28 / among the cleanest air in the country. The city sits at an elevation of 40 feet.
Temperature
38°F Jan (3°C)
64°F Jul (18°C)
| Annual Average | 50.3°F |
| 7% below US avg | |
| January Average | 38°F (3°C) |
| July Average | 64°F (18°C) |
| Sunny Days | 233 days/yr |
Geography
| Elevation | 40 ft (12 m) |
| Area | 0.6 sq mi (1.5 km²) |
| Population Density | 942/sq mi |
| Coordinates | 48.9955°N, 122.2685°W |
| Timezone | America/Los_Angeles |
| County | Island County County |
| Nearest Airport | Bellingham International (BLI) 19 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 28.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Low |
| Risk Score | 78.0 / 100 |
| Social Vulnerability | 36.8 / 100 |
| Community Resilience | 80.4 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Relatively Moderate |
| Wildfire | Very Low |
| Flood | Relatively Low |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Very Low |
| Winter Weather | Relatively Low |
| Lightning | Relatively Low |
| Ice Storm | Relatively Moderate |
| Drought | No Rating |
| Cold Wave | Relatively Low |
| Landslide | Relatively High |
| Coastal Flood | Relatively Moderate |
| Tsunami | Very Low |
| Volcano | Relatively Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
436 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M5.4.
| May 3, 1996 | 8 km NNE of Lake Marcel-Stillwater, Washington | M5.4 | 140 km | 4 km |
| Apr 14, 1990 | 4 km ENE of Deming, Washington | M5.0 | 19 km | 12 km |
| Feb 21, 2025 | 28 km W of Squamish, Canada | M4.8 | 121 km | 10 km |
| Jan 30, 2009 | 6 km ESE of Lofall, Washington | M4.7 | 137 km | 62 km |
| Jul 12, 2019 | 2 km S of Roosevelt, Washington | M4.6 | 126 km | 29 km |
| Mar 3, 2025 | 2025 Orcas Island, Washington | M4.5 | 58 km | 16 km |
| Jun 24, 1997 | 19 km SSW of Gibsons, Canada | M4.4 | 102 km | 3 km |
| Feb 19, 1991 | 31 km E of Squamish, Canada | M4.3 | 85 km | 5 km |
| Apr 2, 1990 | 2 km ENE of Deming, Washington | M4.3 | 19 km | 0 km |
| Sep 21, 2002 | 9 km SW of Friday Harbor, Washington | M4.1 | 85 km | 23 km |
| Apr 14, 1990 | 2 km ESE of Deming, Washington | M4.0 | 20 km | 3 km |
| Apr 3, 1990 | 3 km ENE of Deming, Washington | M4.0 | 19 km | 1 km |
| Dec 27, 2012 | 12 km E of North Saanich, Canada | M4.0 | 81 km | 54 km |
| Sep 26, 2024 | 12 km E of Saanichton, Canada | M4.0 | 85 km | 52 km |
| Jul 1, 2009 | 4 km SE of Coupeville, Washington | M4.0 | 93 km | 58 km |
| Mar 6, 2025 | 14 km SW of Blyn, Washington | M3.9 | 135 km | 42 km |
| Mar 17, 2004 | 3 km SW of Clear Lake, Washington | M3.8 | 61 km | 0 km |
| Sep 8, 2022 | 7 km WNW of Lofall, Washington | M3.7 | 133 km | 23 km |
| Nov 26, 1997 | 15 km WSW of Quilcene, Washington | M3.7 | 146 km | 46 km |
| Dec 11, 1999 | 10 km NNE of Oak Bay, Canada | M3.7 | 88 km | 49 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
5 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF2.
| Date | Rating | Distance | Path | Fatalities |
| May 13, 1986 | EF2 | 88 km | 0.3 mi | 0 |
| Nov 24, 1970 | EF2 | 100 km | 0.3 mi | 0 |
| May 18, 2005 | EF1 | 89 km | 0.2 mi | 0 |
| Jun 5, 2004 | EF0 | 85 km | 0.1 mi | 0 |
| Apr 27, 2004 | EF0 | 4 km | 2.7 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
3 tsunamis recorded within 500 km. Highest wave on record: 38.0 m (125 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 2007 | CHEHALIS LAKE, CHILLIWACK | Meteorological | 38.0 m | — | 56 km |
| 1891 | WASHINGTON | Eruption + Earthquake | 2.4 m | — | 143 km |
| 1820 | CAMANO ISLAND, WA | Meteorological | — | — | 104 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
5 volcanoes within 200 km. Closest: Baker (41 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Baker | Stratovolcano(es) | 3,285 m (10,778 ft) | 1880 | 41 km |
| Garibaldi | Stratovolcano | 2,678 m (8,786 ft) | -8060 | 109 km |
| Garibaldi Lake | Volcanic field | 2,316 m (7,598 ft) | Unknown | 117 km |
| Glacier Peak | Stratovolcano | 3,213 m (10,541 ft) | 1700 | 130 km |
| Cayley Volcanic Field | Volcanic field | 2,375 m (7,792 ft) | Unknown | 145 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
12 wildfires (100+ acres) recorded within 100 km. Largest: SOURDOUGH (7,517 acres, 2023).
| Year | Name | Acres Burned | Distance |
| 2023 | SOURDOUGH | 7,517 | 86 km |
| 2015 | GOODELL | 6,624 | 84 km |
| 2022 | COPPER LAKE | 3,825 | 62 km |
| 2022 | BRUSH CREEK 2 | 3,186 | 65 km |
| 2022 | SILESIA | 2,737 | 56 km |
| 2022 | MCALLISTER CREEK | 2,581 | 95 km |
| 2022 | THREE FOOLS | 2,451 | 100 km |
| 2022 | BOULDER LAKE | 2,347 | 99 km |
| 2022 | LITTLE CHILL | 2,242 | 59 km |
| 2003 | BIGBEAVER | 1,807 | 87 km |
| 1998 | UNNAMED | 1,174 | 81 km |
| 2004 | FREEZEOUT | 1,155 | 96 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 38°F (3°C) | 7.3 in | |
| February | 39°F (4°C) | 5.6 in | |
| March | 42°F (6°C) | 5.3 in | |
| April | 47°F (8°C) | 4.5 in | |
| May | 53°F (12°C) | 3.6 in | |
| June | 58°F (14°C) | 3.1 in | |
| July | 64°F (18°C) | 2.1 in | Warmest |
| August | 63°F (17°C) | 2.1 in | Driest |
| September | 58°F (14°C) | 3.0 in | |
| October | 49°F (10°C) | 5.5 in | |
| November | 41°F (5°C) | 8.5 in | Wettest |
| December | 36°F (2°C) | 7.6 in | Coldest |
Sumas has a seasonal temperature swing of 27°F / from 36°F in December to 64°F in July. Total annual precipitation is 58.0 inches, with November being the wettest month (8.5") and August the driest (2.1").