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Weather & Climate in Index, WA
Temperature, precipitation, air quality, natural hazards, and monthly weather data.
Index experiences four distinct seasons with an average annual temperature of 52°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 68.3 inches (wetter than the 38-inch national average). 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 537 feet.
Temperature
41°F Jan (5°C)
65°F Jul (18°C)
| Annual Average | 51.6°F |
| 4% below US avg | |
| January Average | 41°F (5°C) |
| July Average | 65°F (18°C) |
| Sunny Days | 226 days/yr |
Geography
| Elevation | 537 ft (164 m) |
| Area | 0.1 sq mi (0.2 km²) |
| Population Density | 713/sq mi |
| Coordinates | 47.8213°N, 121.5559°W |
| Timezone | America/Los_Angeles |
| County | King County County |
| Nearest Airport | Seattle Paine Field International (PAE) 35 miles away |
Precipitation & Snow
Air Quality
| AQI Median | 28.0 |
| Rating | Good |
Natural Hazard Risk
| Overall Risk | Very High |
| Risk Score | 99.7 / 100 |
| Social Vulnerability | 14.8 / 100 |
| Community Resilience | 87.4 / 100 |
Hazard Breakdown
| Tornado | Relatively Moderate |
| Earthquake | Very High |
| Wildfire | Relatively Low |
| Flood | Very High |
| Hail | Very Low |
| Strong Wind | Very Low |
| Heat Wave | Relatively High |
| Winter Weather | Relatively High |
| Lightning | Relatively Moderate |
| Ice Storm | Relatively High |
| Drought | Very Low |
| Cold Wave | Relatively Low |
| Landslide | Relatively High |
| Coastal Flood | Relatively Moderate |
| Tsunami | Relatively Low |
| Volcano | Relatively High |
| Avalanche | Very High |
Source: FEMA National Risk Index v1.20 (Dec 2025)
Earthquake History
787 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 | 115 km | 52 km |
| May 3, 1996 | 8 km NNE of Lake Marcel-Stillwater, Washington | M5.4 | 25 km | 4 km |
| Jan 29, 1995 | 3 km WSW of Des Moines, Washington | M5.0 | 78 km | 15 km |
| Apr 14, 1990 | 4 km ENE of Deming, Washington | M5.0 | 122 km | 12 km |
| Jun 23, 1997 | 2 km NE of Enetai, Washington | M4.9 | 80 km | 13 km |
| Apr 25, 2003 | 26 km W of Brinnon, Washington | M4.8 | 128 km | 51 km |
| Jan 30, 2009 | 6 km ESE of Lofall, Washington | M4.7 | 77 km | 62 km |
| Jun 24, 1997 | 16 km WNW of Malott, Washington | M4.6 | 138 km | 10 km |
| Jul 12, 2019 | 2 km S of Roosevelt, Washington | M4.6 | 35 km | 29 km |
| Mar 3, 2025 | 2025 Orcas Island, Washington | M4.5 | 128 km | 16 km |
| Jul 22, 2001 | 4 km WSW of DuPont, Washington | M4.3 | 118 km | 52 km |
| Jun 18, 1994 | 11 km SE of Skykomish, Washington | M4.3 | 31 km | -1 km |
| Apr 2, 1990 | 2 km ENE of Deming, Washington | M4.3 | 122 km | 0 km |
| Jun 27, 2013 | 25 km N of Leavenworth, Washington | M4.3 | 65 km | 8 km |
| Feb 18, 2015 | 15 km ENE of Cle Elum, Washington | M4.2 | 88 km | 4 km |
| May 20, 1995 | 15 km NNE of Ashford, Washington | M4.1 | 109 km | 12 km |
| Sep 21, 2002 | 9 km SW of Friday Harbor, Washington | M4.1 | 138 km | 23 km |
| Feb 23, 2017 | 11 km NE of Hoodsport, Washington | M4.1 | 117 km | 15 km |
| Aug 16, 2004 | 16 km ENE of Packwood, Washington | M4.0 | 128 km | -1 km |
| Apr 14, 1990 | 2 km ESE of Deming, Washington | M4.0 | 121 km | 3 km |
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.
Tornado History
20 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF3. Total: 1 injury.
| Date | Rating | Distance | Path | Fatalities |
| Dec 12, 1969 | EF3 | 73 km | 3.8 mi | 0 |
| Dec 18, 2018 | EF2 | 88 km | 1.4 mi | 0 |
| May 13, 1986 | EF2 | 58 km | 0.3 mi | 0 |
| Nov 24, 1970 | EF2 | 57 km | 0.3 mi | 0 |
| Jan 18, 2015 | EF1 | 95 km | 4.1 mi | 0 |
| Sep 6, 2009 | EF1 | 83 km | 9.6 mi | 0 |
| May 18, 2005 | EF1 | 67 km | 0.2 mi | 0 |
| Jun 27, 2001 | EF1 | 85 km | 2.3 mi | 0 |
| May 31, 1997 | EF1 | 94 km | 0.5 mi | 0 |
| Jun 12, 1978 | EF1 | 98 km | 1.5 mi | 0 |
| Dec 22, 1971 | EF1 | 75 km | 0.5 mi | 0 |
| Oct 26, 1971 | EF1 | 32 km | 3.0 mi | 0 |
| Sep 28, 1962 | EF1 | 66 km | 0.1 mi | 0 |
| Jun 16, 2006 | EF0 | 14 km | 0.5 mi | 0 |
| Jun 5, 2004 | EF0 | 69 km | 0.1 mi | 0 |
| Jun 11, 2001 | EF0 | 76 km | — | 0 |
| Aug 24, 1997 | EF0 | 42 km | 0.5 mi | 0 |
| Jun 23, 1996 | EF0 | 92 km | 0.4 mi | 0 |
| Apr 9, 1991 | EF0 | 85 km | 0.8 mi | 0 |
| Aug 18, 1964 | EF0 | 54 km | 5.2 mi | 0 |
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).
Tsunami History
5 tsunamis recorded within 500 km. Highest wave on record: 3.0 m (10 ft).
| Year | Location | Cause | Max Wave | Deaths | Distance |
| 1894 | PUYALLUP RIVER DELTA, TACOMA, WA | Meteorological | 3.0 m | 2 | 89 km |
| 1891 | WASHINGTON | Eruption + Earthquake | 2.4 m | — | 146 km |
| 1949 | PUGET SOUND, WA | Meteorological | 2.4 m | — | 94 km |
| 1949 | PUGET SOUND, WA | Eruption + Earthquake | — | 8 | 108 km |
| 1820 | CAMANO ISLAND, WA | Meteorological | — | — | 66 km |
Source: NOAA/NCEI Historical Tsunami Database.
Nearby Volcanoes
5 volcanoes within 200 km. Closest: Glacier Peak (46 km).
| Name | Type | Elevation | Last Eruption | Distance |
| Glacier Peak | Stratovolcano | 3,213 m (10,541 ft) | 1700 | 46 km |
| Baker | Stratovolcano(es) | 3,285 m (10,778 ft) | 1880 | 108 km |
| Rainier | Stratovolcano | 4,392 m (14,409 ft) | 1450 | 109 km |
| Adams | Stratovolcano | 3,742 m (12,277 ft) | 950 | 180 km |
| St. Helens | Stratovolcano | 2,549 m (8,363 ft) | 2008 | 186 km |
Source: Smithsonian Institution Global Volcanism Program (GVP).
Wildfire History
20 wildfires (100+ acres) recorded within 100 km. Largest: TYEE CREEK (123,618 acres, 1994).
| Year | Name | Acres Burned | Distance |
| 1994 | TYEE CREEK | 123,618 | 88 km |
| 2015 | WOLVERINE | 66,329 | 75 km |
| 2012 | TABLE MOUNTAIN COMPLEX | 65,887 | 97 km |
| 2001 | REX CREEK COMPLEX (REX CREEK) | 54,456 | 90 km |
| 2017 | NORSE PEAK | 51,017 | 92 km |
| 2018 | COUGAR CREEK | 42,681 | 81 km |
| 2017 | JOLLY MOUNTAIN | 38,159 | 69 km |
| 2004 | POT PEAK-SISI RIDGE COMPLEX | 37,603 | 89 km |
| 1988 | DINKELMAN | 36,246 | 91 km |
| 1994 | HATCHERY COMPLEX (RAT) | 27,265 | 71 km |
| 2021 | TWENTYFIVE MILE | 23,379 | 93 km |
| 2014 | MILLS CANYON | 21,952 | 97 km |
| 2004 | FISCHER | 16,197 | 82 km |
| 2010 | SWAKANE | 16,049 | 97 km |
| 2022 | BOLT CREEK | 15,211 | 12 km |
| 2014 | CHIWAUKUM COMPLEX | 14,511 | 59 km |
| 1994 | HATCHERY COMPLEX (HATCHERY) | 13,976 | 65 km |
| 2014 | DUNCAN | 13,714 | 76 km |
| 2021 | RED APPLE | 12,540 | 95 km |
| 2007 | DOMKE LAKE COMPLEX | 10,090 | 80 km |
Source: NIFC/IRWIN Wildfire Records (100+ acres).
Monthly Weather
| Month | Avg Temperature | Precipitation | Summary |
|---|---|---|---|
| January | 41°F (5°C) | 13.4 in | |
| February | 35°F (1°C) | 9.7 in | |
| March | 37°F (3°C) | 8.7 in | |
| April | 42°F (5°C) | 6.6 in | |
| May | 48°F (9°C) | 4.7 in | |
| June | 53°F (12°C) | 3.6 in | |
| July | 65°F (18°C) | 2.0 in | Warmest, Driest |
| August | 60°F (15°C) | 2.3 in | |
| September | 55°F (13°C) | 4.4 in | |
| October | 46°F (8°C) | 7.7 in | |
| November | 37°F (3°C) | 13.3 in | |
| December | 32°F (-0°C) | 13.7 in | Coldest, Wettest |
Index has a seasonal temperature swing of 33°F / from 32°F in December to 65°F in July. Total annual precipitation is 89.9 inches, with December being the wettest month (13.7") and July the driest (2.0").