Seattle, Washington climate: Normal weather by month, frost dates and records
Seattle's normal year runs from 37°F December nights to 78°F August afternoons, with 39.3 inches of precipitation and 6 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.1°C, December lows of 3°C, August highs of 25°C, 999 mm of precipitation a year.
- NOAA stationSeattle Tacoma International Airport
- Station IDUSW00024233
- Location47.44°N 122.31°W
- Elevation370 ft (113 m)
- From the center12 miles
- Population780,995
On October 23, the normal high in Seattle is 58°F and the normal low 45°F, and the chance of measurable rain or snow is 50%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Seattle.
- Jan 48° 38°
- Feb 50° 38°
- Mar 54° 40°
- Apr 59° 43°
- May 66° 49°
- Jun 71° 53°
- Jul 77° 57°
- Aug 78° 57°
- Sep 72° 54°
- Oct 61° 47°
- Nov 52° 41°
- Dec 47° 37°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Seattle each month?
August is the warmest month, with normal highs of 78°F; December the coldest, with normal lows of 37°F. The most precipitation falls in November (6.31 in), the least in July (0.60 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 48°F | 38°F | 42.8°F | 5.78 | 1.8 | 19 | <1 | 7 | 8 h 50 min |
| February | 50°F | 38°F | 44.0°F | 3.76 | 2.2 | 16 | <1 | 6 | 10 h 10 min |
| March | 54°F | 40°F | 47.1°F | 4.17 | 0.4 | 17 | <1 | 2 | 11 h 50 min |
| April | 59°F | 43°F | 51.3°F | 3.18 | 0.0 | 15 | <1 | <1 | 13 h 30 min |
| May | 66°F | 49°F | 57.5°F | 1.88 | 0.0 | 11 | <1 | <1 | 15 h 10 min |
| June | 71°F | 53°F | 62.0°F | 1.45 | 0.0 | 9 | 1 | <1 | 16 h |
| July | 77°F | 57°F | 67.1°F | 0.60 | 0.0 | 5 | 2 | <1 | 15 h 40 min |
| August | 78°F | 57°F | 67.4°F | 0.97 | 0.0 | 5 | 1 | <1 | 14 h 20 min |
| September | 72°F | 54°F | 62.6°F | 1.61 | 0.0 | 8 | <1 | <1 | 12 h 40 min |
| October | 61°F | 47°F | 53.8°F | 3.91 | 0.0 | 14 | <1 | <1 | 11 h |
| November | 52°F | 41°F | 46.5°F | 6.31 | 0.2 | 18 | <1 | 3 | 9 h 20 min |
| December | 47°F | 37°F | 42.0°F | 5.72 | 1.7 | 18 | <1 | 7 | 8 h 30 min |
| Year (annual) | 61°F | 46°F | 53.7°F | 39.34 | 6.3 | 156 | 4 | 25 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 9°C | 3°C | 6.0°C | 147 mm | 5 cm |
| February | 10°C | 3°C | 6.7°C | 96 mm | 6 cm |
| March | 12°C | 4°C | 8.4°C | 106 mm | 1 cm |
| April | 15°C | 6°C | 10.7°C | 81 mm | 0 cm |
| May | 19°C | 9°C | 14.2°C | 48 mm | 0 cm |
| June | 22°C | 12°C | 16.7°C | 37 mm | 0 cm |
| July | 25°C | 14°C | 19.5°C | 15 mm | 0 cm |
| August | 25°C | 14°C | 19.7°C | 25 mm | 0 cm |
| September | 22°C | 12°C | 17.0°C | 41 mm | 0 cm |
| October | 16°C | 8°C | 12.1°C | 99 mm | 0 cm |
| November | 11°C | 5°C | 8.1°C | 160 mm | 1 cm |
| December | 8°C | 3°C | 5.6°C | 145 mm | 4 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024233; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Seattle?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, July has the fewest days with rain (5).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024233.
When is the last frost in Seattle?
In Seattle, the last spring frost (32°F) comes after March 2 in half of years and after March 23 in one year in ten; the first autumn frost comes before November 23 in half of years and before November 6 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 21 year in 10 after March 23; 9 in 10 after February 5
- First autumn frost, half of years before
- November 231 year in 10 before November 6; 9 in 10 before December 15
NOAA puts the median frost-free season at 266 days, and the season without a hard freeze (28°F) at 315 days.
A hard freeze (28°F) comes after February 4 in half of springs and before December 10 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Seattle in zone 9a across its 28 ZIP code areas (9a in 98115, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Seattle's NOAA station is in zone 9a: the coldest night of a typical year reaches 22°F (30 complete years).
Frost dates for every NOAA station in Washington · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00024233; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
What hardiness zone is each Seattle ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Seattle's 28 ZIP code areas are all in zone 9a. Each ZIP's frost dates are in the frost tool.
| ZIP code | Zone | Land in Seattle |
|---|---|---|
| 98101 | 9a | 1.4 km² |
| 98102 | 9a | 3.3 km² |
| 98103 | 9a | 11.9 km² |
| 98104 | 9a | 2.5 km² |
| 98105 | 9a | 9.9 km² |
| 98106 | 9a | 13.4 km² |
| 98107 | 9a | 5.6 km² |
| 98108 | 9a | 15.8 km² |
| 98109 | 9a | 5.0 km² |
| 98112 | 9a | 8.3 km² |
| 98115 | 9a | 17.0 km² |
| 98116 | 9a | 7.8 km² |
| 98117 | 9a | 10.0 km² |
| 98118 | 9a | 16.2 km² |
| 98119 | 9a | 6.2 km² |
| 98121 | 9a | 1.1 km² |
| 98122 | 9a | 6.0 km² |
| 98125 | 9a | 14.1 km² |
| 98126 | 9a | 7.9 km² |
| 98133 | 9a | 7.7 km² |
| 98134 | 9a | 8.6 km² |
| 98136 | 9a | 5.9 km² |
| 98144 | 9a | 8.7 km² |
| 98146 | 9a | 2.4 km² |
| 98177 | 9a | 5.7 km² |
| 98178 | 9a | 2.8 km² |
| 98195 | 9a | 1.0 km² |
| 98199 | 9a | 11.0 km² |
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Seattle?
In a normal year in Seattle, 4 days a year reach 90°F, 25 nights fall to 32°F or colder and 156 days bring measurable precipitation.
- Days at 90°F or more
- 4a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 25a normal year
- Days that stay below freezing
- 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 156a normal year
- Days with 1 inch of snow or more
- 2a normal year
The highest temperature in this station's record (since 1945) is 108°F, on June 28, 2021; the lowest is 0°F, on January 31, 1950.
The wettest calendar year on that record is 1950, with 55.14 in; the snowiest season is 1968–69, with 67.5 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00024233; records: ACIS (NOAA Regional Climate Centers), station USW00024233. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Seattle, and how clear are its skies?
The summer (June-August) dew point averages 52°F. The muggiest month is July, with an average dew point of 54°F; the driest air comes in December (35°F). December is the windiest month (8.4 mph on average), and July has the most clear or nearly clear hours (51%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 36°F | 78% | 69% | 8.3 mph | 19% | 53% |
| February | 36°F | 74% | 61% | 8.3 mph | 20% | 46% |
| March | 39°F | 72% | 57% | 8.3 mph | 17% | 46% |
| April | 42°F | 68% | 52% | 8.0 mph | 20% | 38% |
| May | 48°F | 68% | 52% | 7.4 mph | 21% | 34% |
| June | 51°F | 65% | 48% | 7.3 mph | 32% | 25% |
| July | 54°F | 64% | 45% | 6.8 mph | 51% | 19% |
| August | 52°F | 67% | 47% | 6.8 mph | 40% | 20% |
| September | 49°F | 75% | 57% | 6.8 mph | 40% | 28% |
| October | 42°F | 79% | 68% | 7.6 mph | 24% | 46% |
| November | 36°F | 79% | 72% | 8.4 mph | 17% | 52% |
| December | 35°F | 79% | 73% | 8.4 mph | 16% | 59% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024233. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Seattle?
Over a year 67% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Seattle, 3.4 kWh per square metre a day. August is the sunniest month (78%) and December the cloudiest (51%). Among the 459 U.S. places of 50,000 or more, that ranks tied 452nd (with 6 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 52% | 1.0 |
| February | 60% | 1.9 |
| March | 58% | 2.9 |
| April | 63% | 4.2 |
| May | 66% | 5.3 |
| June | 68% | 5.7 |
| July | 78% | 6.3 |
| August | 78% | 5.4 |
| September | 74% | 3.9 |
| October | 63% | 2.3 |
| November | 54% | 1.2 |
| December | 51% | 0.8 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Seattle need?
A normal year in Seattle brings 4,376 heating degree days, 19% fewer than the median U.S. place (5,373), and 265 cooling degree days, 71% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,324 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 687 | 0 |
| February | 588 | 0 |
| March | 557 | 0 |
| April | 412 | 1 |
| May | 242 | 9 |
| June | 118 | 29 |
| July | 31 | 96 |
| August | 24 | 98 |
| September | 102 | 30 |
| October | 349 | 1 |
| November | 555 | 0 |
| December | 711 | 0 |
| Year (annual) | 4,376 | 265 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024233. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Seattle been warmer than normal lately?
2025 averaged 53.9°F, 0.2°F above the 1991-2020 normal of 53.7°F. 2 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 53.5°F | −0.2°F | 43.33 | 21.6 |
| 2022 | 52.7°F | −1.0°F | 40.93 | 5.8 |
| 2023 | 53.8°F | +0.1°F | 34.97 | 2.3 |
| 2024 | 53.6°F | −0.1°F | 32.17 | 0.3 |
| 2025 | 53.9°F | +0.2°F | 33.05 | 2.3 |
Over 76 complete years from 1950 to 2025, the station's annual mean temperature rose at a fitted 3.4°F per century (+0.19°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00024233; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Seattle's climate compare?
Seattle is warmer than 91 of the other 95 places with their own NOAA record in Washington, and wetter than 57. Across the 7,247 U.S. stations with normals, its annual mean of 53.7°F is warmer than 56%.
In the Köppen classification computed from these normals, Seattle is Csb: temperate, dry-summer, warm summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Seattle share this climate record?
6 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Burien, WAalso near: Seattle Boeing Field (4 mi, 53.8°F a year); Renton (6 mi, 53.6°F a year)52,046 people · 3 mi NW
- SeaTac, WA34,024 people · 1 mi E
- Des Moines, WA33,207 people · 4 mi S
- Tukwila, WA21,636 people · 3 mi NE
- Vashon, WA10,424 people · 7 mi W
- Normandy Park, WA6,661 people · 2 mi SW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Seattle's other NOAA stations record?
2 more NOAA stations keep 1991-2020 normals in or near Seattle. This page uses Seattle Tacoma International Airport; the others differ by site and elevation, and the linked ones have pages of their own:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Seattle Boeing Field USW00024234 | 7 mi S | 20 ft | 53.8°F | 37°F | 77°F | 36.5 | – | March 13 |
| Seattle Sand Point Weather Office USW00094290 | 6 mi NE | 60 ft | 53.2°F | 37°F | 77°F | 37.8 | 4 | March 8 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Seattle's climate
What is the coldest month in Seattle?
December, with a normal high of 47°F and a normal low of 37°F. The warmest is August (78°F by day, 57°F at night).
Does it snow in Seattle?
Yes: 6 inches in a normal year, falling on 5 days with 0.1 inch or more, the most in February (2.2 inches).
What is the rainiest month in Seattle?
November, with 6.31 in of precipitation in a normal year; the driest is July with 0.60 in.
What plant hardiness zone is Seattle in?
The USDA's 2023 map puts Seattle in zone 9a across its 28 ZIP code areas (9a in 98115, the largest). By the same method at Seattle's NOAA station, the coldest night of a typical year reaches 22°F (30 years, 1991-2020): zone 9a.
How late can frost come in Seattle?
In half of years the last 32°F night comes after March 2; in one year in ten it comes after March 23. Waiting until March 23 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Seattle in OctoberThis month day by day, its records and recent years
- Washington climateThe statewide normals and every place in the state
- Kent, WA4 miles from this station, 53.8°F a year
- Renton, WA6 miles from this station, 53.6°F a year
- Seattle Boeing Field, WA6 miles from this station, 53.8°F a year
- Tacoma #1, WA14 miles from this station, 53.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made