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Weather & Climate in Union, WA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Union experiences four distinct seasons with an average annual temperature of 51°F (11°C). Winters average 41°F in January while summers reach 65°F in July. The area gets 226 sunny days per year, above the national average. Annual precipitation totals 92.0 inches (wetter than the 38-inch national average). The area receives 4.4 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 341 feet.
Temperature
41°F Jan (5°C)
65°F Jul (18°C)
| Annual Average | 51.3°F |
| 5% below US avg | |
| January Average | 41°F (5°C) |
| July Average | 65°F (18°C) |
| Sunny Days | 226 days/yr |
Geography
| Elevation | 341 ft (104 m) |
| Area | 1.6 sq mi (4.2 km²) |
| Population Density | 173/sq mi |
| Coordinates | 47.3475°N, 123.0951°W |
| Timezone | America/Los_Angeles |
| County | Mason County County |
| Nearest Airport | Olympia Regional (OLM) 28 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 28.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Relatively Moderate |
| Risk Score | 85.3 / 100 |
| Social Vulnerability | 70.5 / 100 |
| Community Resilience | 39.4 / 100 |
Hazard Breakdown
| Tornado | Very Low |
| Earthquake | Relatively Moderate |
| Wildfire | Very Low |
| Flood | Relatively Moderate |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Relatively Low |
| Winter Weather | Relatively Low |
| Lightning | Very Low |
| Ice Storm | Very Low |
| Drought | Very Low |
| Cold Wave | No Rating |
| Landslide | Relatively High |
| Coastal Flood | Relatively Moderate |
| Tsunami | Very Low |
| Volcano | Very Low |
| Avalanche | Very Low |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
1,410 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M6.8.
| Feb 28, 2001 | 7 km SSE of Longbranch, Washington | M6.8 | 36 km | 52 km |
| Jul 3, 1999 | 8 km N of Satsop, Washington | M5.8 | 41 km | 40 km |
| May 3, 1996 | 8 km NNE of Lake Marcel-Stillwater, Washington | M5.4 | 102 km | 4 km |
| Jun 10, 2001 | 18 km N of Satsop, Washington | M5.0 | 37 km | 40 km |
| Jan 29, 1995 | 3 km WSW of Des Moines, Washington | M5.0 | 55 km | 15 km |
| Jun 23, 1997 | 2 km NE of Enetai, Washington | M4.9 | 48 km | 13 km |
| Apr 25, 2003 | 26 km W of Brinnon, Washington | M4.8 | 38 km | 51 km |
| Jan 30, 2009 | 6 km ESE of Lofall, Washington | M4.7 | 62 km | 62 km |
| Jul 12, 2019 | 2 km S of Roosevelt, Washington | M4.6 | 100 km | 29 km |
| Mar 3, 2025 | 2025 Orcas Island, Washington | M4.5 | 142 km | 16 km |
| Jun 18, 1994 | 11 km SE of Skykomish, Washington | M4.3 | 141 km | -1 km |
| Jul 22, 2001 | 4 km WSW of DuPont, Washington | M4.3 | 42 km | 52 km |
| Feb 14, 2011 | 31 km S of Morton, Washington | M4.3 | 136 km | 4 km |
| May 20, 1995 | 15 km NNE of Ashford, Washington | M4.1 | 102 km | 12 km |
| Sep 21, 2002 | 9 km SW of Friday Harbor, Washington | M4.1 | 127 km | 23 km |
| Feb 23, 2017 | 11 km NE of Hoodsport, Washington | M4.1 | 15 km | 15 km |
| Aug 16, 2004 | 16 km ENE of Packwood, Washington | M4.0 | 144 km | -1 km |
| Jun 15, 1994 | 1 km WNW of Hoodsport, Washington | M4.0 | 9 km | 44 km |
| Sep 26, 2024 | 12 km E of Saanichton, Canada | M4.0 | 138 km | 52 km |
| Dec 27, 2012 | 12 km E of North Saanich, Canada | M4.0 | 146 km | 54 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
28 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 1 injury.
| Date | Rating | Distance | Path | Fatalities |
| Dec 12, 1969 | EF3 | 55 km | 3.8 mi | 0 |
| Dec 18, 2018 | EF2 | 39 km | 1.4 mi | 0 |
| Nov 10, 1965 | EF2 | 74 km | 1.5 mi | 0 |
| Oct 10, 2020 | EF1 | 64 km | 0.5 mi | 0 |
| Oct 18, 2019 | EF1 | 14 km | 0.7 mi | 0 |
| Jan 18, 2015 | EF1 | 38 km | 4.1 mi | 0 |
| Sep 30, 2013 | EF1 | 63 km | 1.0 mi | 0 |
| Sep 6, 2009 | EF1 | 74 km | 9.6 mi | 0 |
| May 27, 2004 | EF1 | 59 km | 0.2 mi | 0 |
| Jun 27, 2001 | EF1 | 72 km | 2.3 mi | 0 |
| May 31, 1997 | EF1 | 50 km | 0.5 mi | 0 |
| Jun 12, 1978 | EF1 | 60 km | 1.5 mi | 0 |
| Dec 22, 1971 | EF1 | 58 km | 0.5 mi | 0 |
| Sep 28, 1962 | EF1 | 62 km | 0.1 mi | 0 |
| Apr 27, 2014 | EF0 | 83 km | 0.2 mi | 0 |
| May 27, 2011 | EF0 | 87 km | 0.1 mi | 0 |
| Jan 28, 2006 | EF0 | 49 km | 0.5 mi | 0 |
| Oct 15, 2003 | EF0 | 60 km | 0.1 mi | 0 |
| Jun 11, 2001 | EF0 | 52 km | — | 0 |
| Dec 23, 1997 | EF0 | 94 km | 0.3 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
6 tsunamis recorded within 500 km. Highest wave on record: 250.0 m (820 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1980 | WASHINGTON | Explosion | 250.0 m | 61 | 145 km |
| 1894 | PUYALLUP RIVER DELTA, TACOMA, WA | Meteorological | 3.0 m | 2 | 50 km |
| 1891 | WASHINGTON | Eruption + Earthquake | 2.4 m | — | 79 km |
| 1949 | PUGET SOUND, WA | Meteorological | 2.4 m | — | 43 km |
| 1949 | PUGET SOUND, WA | Eruption + Earthquake | — | 8 | 41 km |
| 1820 | CAMANO ISLAND, WA | Meteorological | — | — | 96 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
7 volcanoes within 200 km. Closest: Rainier (115 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Rainier | Stratovolcano | 4,392 m (14,409 ft) | 1450 | 115 km |
| St. Helens | Stratovolcano | 2,549 m (8,363 ft) | 2008 | 145 km |
| Glacier Peak | Stratovolcano | 3,213 m (10,541 ft) | 1700 | 171 km |
| Adams | Stratovolcano | 3,742 m (12,277 ft) | 950 | 176 km |
| West Crater | Volcanic field | 1,329 m (4,360 ft) | -5750 | 181 km |
| Indian Heaven | Shield(s) | 1,806 m (5,925 ft) | -6250 | 185 km |
| Baker | Stratovolcano(es) | 3,285 m (10,778 ft) | 1880 | 185 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
7 wildfires (100+ acres) recorded within 100 km. Largest: DELABARRE (4,176 acres, 2023).
| Year | Name | Acres Burned | Distance |
| 2023 | DELABARRE | 4,176 | 55 km |
| 2018 | MAPLE | 3,547 | 26 km |
| 2015 | PARADISE | 2,818 | 66 km |
| 2016 | HAYES TWO | 2,679 | 55 km |
| 2011 | BIG HUMP | 1,400 | 39 km |
| 1985 | BEAVER | 1,107 | 29 km |
| 2006 | BEAR GULCH II | 1,037 | 23 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 41°F (5°C) | 9.3 in | |
| February | 41°F (5°C) | 7.6 in | |
| March | 44°F (7°C) | 6.9 in | |
| April | 48°F (9°C) | 4.2 in | |
| May | 53°F (12°C) | 2.7 in | |
| June | 57°F (14°C) | 1.9 in | |
| July | 65°F (18°C) | 1.1 in | Warmest, Driest |
| August | 62°F (17°C) | 1.4 in | |
| September | 58°F (15°C) | 2.5 in | |
| October | 51°F (10°C) | 5.2 in | |
| November | 44°F (7°C) | 9.6 in | |
| December | 39°F (4°C) | 10.4 in | Coldest, Wettest |
Union has a seasonal temperature swing of 25°F / from 39°F in December to 65°F in July. Total annual precipitation is 62.8 inches, with December being the wettest month (10.4") and July the driest (1.1").