Seattle Climate chart (explanation) J F M A M J J A S O N D 5.2 48 38 3.9 50 38 3.3 54 40 2 59 43 1.5 66 49 1.4 71 53 0.6 77 57 0.8 78 57 1.6 72 54 3.9 61 47 6.3 52 41 5.7 47 37 █ Average max. and min. temperatures in °F █ Precipitation totals in inchesSource: [1] Metric conversion J F M A M J J A S O N D 132 9 3 99 10 3 84 12 4 50 15 6 38 19 9 36 22 12 16 25 14 19 26 14 41 22 12 99 16 8 160 11 5 145 8 3 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Rainy day in Capitol Hill, Seattle. Seattle experiences around 150 days with at least 0.01 inches (0.25 mm) precipitation each year.
The climate of Seattle is temperate, classified in the warm-summer (in contrast to hot-summer) subtype of the Mediterranean zone by the most common climate classification (Köppen: Csb)[2][3][4] although some sources put the city in the oceanic zone (Trewartha: Do).[5][6] It has cool, wet winters and warm, dry summers, covering characteristics of both.[7][8] The climate is sometimes characterized as a "modified Mediterranean" climate because it is cooler and wetter than a "true" Mediterranean climate, but shares the characteristic dry summer and the associated reliance upon cooler-season precipitation (which has a strong influence on the region's vegetation).[9] The city is part of USDA hardiness zone 9a, with surrounding pockets falling under 8b.[10]
Records for the Seattle City area date back to 1894, with records at Seattle-Tacoma International Airport beginning in 1945, a location notably not within Seattle. Prior to 1945 the official temperatures were observed in locations in downtown Seattle, which tends in general to be somewhat warmer and drier than the airport location.[11] The hottest officially recorded temperature was 108 °F (42 °C) on June 28, 2021; the coldest recorded temperature was 0 °F (−18 °C) on January 31, 1950;[12] the record cold daily maximum is 16 °F (−9 °C) on January 14, 1950, while, conversely, the record warm daily minimum is 73 °F (23 °C) on June 27, 2021.[13]
Seattle generally does not experience many extremes of weather. However, the 21st century has seen a trend towards more extreme high-temperature and large-precipitation events. In July 2009 Seattle's all-time high temperature was broken by a margin of 4 degrees Fahrenheit (2.2 Celsius),[14] then broken again by a margin of 5 F (2.8 C) in June 2021. The single-day precipitation record set in October 2003 saw higher precipitation by nearly 2 inches (50mm) than any other day on record. However, thunderstorms are still rare,[15] as the city reports thunder on just seven days per year.[16] Similarly, the city typically receives at least light snowfall every year, though hey snowfall is uncommon.
Temperature[edit] Weather report from Seattle-Tacoma Airport in June 2021. Seattle recorded its highest temperature ever on June 28, reaching 108 °F (42 °C).[17]The city's regime of temperature features small seasonal swings, due to its proximity to the ocean. The Pacific Ocean, Puget Sound and Lake Washington serve as moderators of the temperature meaning the city is milder than areas inland during the winter and cooler during the summer. Extreme heatwes are rare, as are cold temperatures. Hot temperature extremes are enhanced by dry, compressed wind from the west slopes of the Cascades,[18] while cold temperatures are generated mainly from the Fraser Valley in British Columbia.[19] Records are taken from the Seattle City area from 1894 to 1944 and at Sea-Tac Airport from 1945.
Averages[edit]In an erage year, the temperature will usually be between 21 °F (−6 °C) and 94 °F (34 °C) with temperatures greatly exceeding these values being uncommon. Temperatures above 97 °F (36 °C) and below 15 °F (−9 °C) are very rare, with the last occurrences being June 28, 2021 and November 24, 2010, respectively.[13]
Climate data for Seattle (Seattle-Tacoma International Airport), 1991–2020 normals Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean maximum °F (°C) 57.0(13.9) 59.1(15.1) 66.4(19.1) 74.3(23.5) 81.9(27.7) 85.8(29.9) 91.2(32.9) 89.9(32.2) 84.1(28.9) 72.0(22.2) 61.6(16.4) 56.8(13.8) 94.1(34.5) Mean daily maximum °F (°C) 48.0(8.9) 50.3(10.2) 54.2(12.3) 59.3(15.2) 66.3(19.1) 71.1(21.7) 77.4(25.2) 77.6(25.3) 71.6(22.0) 60.5(15.8) 52.1(11.2) 47.0(8.3) 61.3(16.3) Daily mean °F (°C) 42.8(6.0) 44.0(6.7) 47.1(8.4) 51.3(10.7) 57.5(14.2) 62.0(16.7) 67.1(19.5) 67.4(19.7) 62.6(17.0) 53.8(12.1) 46.5(8.1) 42.0(5.6) 53.7(12.1) Mean daily minimum °F (°C) 37.7(3.2) 37.7(3.2) 39.9(4.4) 43.3(6.3) 48.7(9.3) 53.0(11.7) 56.8(13.8) 57.2(14.0) 53.6(12.0) 47.0(8.3) 40.9(4.9) 37.1(2.8) 46.1(7.8) Mean minimum °F (°C) 26.1(−3.3) 27.3(−2.6) 31.3(−0.4) 35.6(2.0) 40.6(4.8) 46.6(8.1) 51.5(10.8) 51.7(10.9) 45.8(7.7) 36.8(2.7) 29.2(−1.6) 25.4(−3.7) 21.5(−5.8) Source: NOAA[13] Highest daily temperatures[edit] Period Record temperature[13] Date January 67 °F (19 °C) Jan 28, 1931 February 70 °F (21 °C) Feb 27, 1968 March 79 °F (26 °C) Mar 20, 2019Mar 19, 2019 April 89 °F (32 °C) Apr 18, 2016 May 93 °F (34 °C) May 21, 1963 June 108 °F (42 °C) Jun 28, 2021 July 103 °F (39 °C) Jul 29, 2009 August 99 °F (37 °C) Aug 9, 1981Aug 9, 1960 September 98 °F (37 °C) Sep 2, 1988 October 89 °F (32 °C) Oct 1, 1987 November 74 °F (23 °C) Nov 3, 2010Nov 4, 1949 December 66 °F (19 °C) Dec 10, 2014 Lowest daily temperatures[edit] Period Record temperature Date January 0 °F (−18 °C) Jan 31, 1950 February −1 °F (−18 °C) Feb 1, 1950 March 11 °F (−12 °C) Mar 4, 1955 April 29 °F (−2 °C) Apr 5, 1975Apr 1, 1953Apr 7–8, 1952Apr 21, 1951 May 28 °F (−2 °C) May 1, 1954 June 38 °F (3 °C) Jun 12, 1952 July 43 °F (6 °C) Jul 4, 1949Jul 24, 1953Jul 2, 1954 August 44 °F (7 °C) Aug 13–14, 1955Aug 27, 1952Aug 29, 1951Aug 4, 1950Aug 21, 1947 September 35 °F (2 °C) Sep 27, 1972 October 28 °F (−2 °C) Oct 19, 1949 November 6 °F (−14 °C) Nov 15, 1955 December 6 °F (−14 °C) Dec 30, 1968Daily record warm minima[edit] Period Record temperature Date January 54 °F (12 °C) Jan 24, 1935 February 54 °F (12 °C) Feb 28, 1901 March 59 °F (15 °C) Mar 19, 2019 April 57 °F (14 °C) Apr 28, 1976 May 65 °F (18 °C) May 15, 2023 May 9, 1940 June 73 °F (23 °C) Jun 27, 2021 July 71 °F (22 °C) Jul 29, 2009 August 71 °F (22 °C) Aug 14, 2023 September 69 °F (21 °C) Sep 2, 1974 October 63 °F (17 °C) Oct 18, 1940 November 58 °F (14 °C) Nov 4, 2020 December 55 °F (13 °C) Dec 26, 1980Dec 28, 1917 Daily record cold maxima[edit] Period Record temperature Date January 16 °F (−9 °C) Jan 14, 1950 February 18 °F (−8 °C) Feb 2, 1989 March 29 °F (−2 °C) Mar 4, 1955 April 41 °F (5 °C) Apr 3, 1920Apr 11, 1911 May 46 °F (8 °C) May 15, 1894 June 50 °F (10 °C) Jun 1, 1908 July 54 °F (12 °C) Jul 2, 1966 August 54 °F (12 °C) Aug 2, 1956 September 49 °F (9 °C) Sep 26, 1948 October 35 °F (2 °C) Oct 30, 1935 November 21 °F (−6 °C) Nov 12, 1955 December 17 °F (−8 °C) Dec 29, 1968
Highest erages[edit] Period Record mean Year Year 55.6 °F (13.1 °C) 1940, 2015 Spring (March–May) 55.8 °F (13.2 °C) 1934 Summer (June–August) 69.2 °F (20.7 °C) 2015 Autumn (September–November) 57.4 °F (14.1 °C) 1967 Winter (December–February) 46.9 °F (8.3 °C) 1940–1941 January 47.0 °F (8.3 °C) 2010 February 48.8 °F (9.3 °C) 2015 March 53.1 °F (11.7 °C) 1941 April 56.7 °F (13.7 °C) 2016 May 61.2 °F (16.2 °C) 2018 June 67.7 °F (19.8 °C) 2015 July 71.2 °F (21.8 °C) 2015 August 71.1 °F (21.7 °C) 1967 September 65.7 °F (18.7 °C) 1967 October 58.0 °F (14.4 °C) 2014 November 51.9 °F (11.1 °C) 1899 December 47.5 °F (8.6 °C) 1939 Lowest erages[edit] Period Record mean Year Year 47.9 °F (8.8 °C) 1955 Spring (March–May) 44.8 °F (7.1 °C) 1955 Summer (June–August) 59.0 °F (15.0 °C) 1954 Autumn (September–November) 48.4 °F (9.1 °C) 1985 Winter (December–February) 34.4 °F (1.3 °C) 1949–1950, 1948–1949 January 24.9 °F (−3.9 °C) 1950 February 35.6 °F (2.0 °C) 1956 March 39.1 °F (3.9 °C) 1955 April 44.6 °F (7.0 °C) 1955 May 50.6 °F (10.3 °C) 1962 June 55.5 °F (13.1 °C) 1953 July 60.0 °F (15.6 °C) 1955 August 60.2 °F (15.7 °C) 1910 September 55.3 °F (12.9 °C) 1972 October 47.7 °F (8.7 °C) 1946 November 35.8 °F (2.1 °C) 1985 December 35.2 °F (1.8 °C) 1990
NOTE: in the tables below, all numbers before 1945 come from locations in downtown Seattle, which tends to be somewhat warmer than the current official location of Sea-Tac airport.[11] To distinguish these older numbers we mark them below in italics.
Precipitation[edit] Cherry Street after hey snowfall on January 10, 1880The city sees frequent, though light rainfall between October and May, with rainfall becoming lighter and sparser between June and September. With many more "rain days" than other major American cities, Seattle has a well-earned reputation for frequent rain.[20] In an erage year, at least 0.01 inches (0.25 mm) of precipitation falls on 150 days, more than nearly all U.S. cities east of the Rocky Mountains. In November, Seattle erages more rainfall than any other U.S. city of more than 250,000 people; it also ranks highly in winter precipitation. Conversely, the city receives some of the lowest precipitation amounts of any large city from June to September. Seattle is one of the five rainiest major U.S. cities as measured by the number of days with precipitation.[21][16] However, because Seattle often has merely a light drizzle falling from the sky for many days, it actually receives significantly less rainfall (or other precipitation) overall than many other U.S. cities like New York City, Miami, or Houston. Seattle experiences its heiest rainfall during November, December, and January, receiving roughly half of its annual rainfall (by volume) during this period. In late fall and early winter, atmospheric rivers (also known as "Pineapple Express" systems), strong frontal systems, and Pacific low-pressure systems are common. Light rain and drizzle are the predominant forms of precipitation during the remainder of the year. On erage, less than 1.6 in (41 mm) of rain falls in July and August combined when rain is less common.
Annually, total precipitation erages 39.3 in (998 mm), with winter being the wettest season and July the driest month. At Sea-Tac, rain has fallen in every month since records began there in January 1945, previously in the Seattle City area, the July's of 1896 and 1922 reported no precipitation. Long stretches of little precipitation can occur. No measurable precipitation, greater than 0.01 inches (0.25 mm), fell between June 18 and August 13, 2017.[22] The city also sees snow, primarily in winter, but sometimes in the late autumn and early spring. Snowfall erages 6.3 in (16.0 cm) per year but is highly variable between winter seasons. The most rainfall in 24 hours was 5.02 in (127.5 mm) on October 20, 2003, and the most snowfall was 21.5 in (55 cm) on February 2, 1916.[13] Seattle typically receives some snowfall on an annual basis but hey snow is rare. Average annual snowfall, as measured at Sea-Tac Airport, is 6.3 inches (16.0 cm). From winter season to winter season, amounts can be extremely variable.
Due to local variations in microclimate, Seattle also receives significantly lower precipitation than some other locations west of the Cascades. Around 80 mi (130 km) to the west, the Hoh Rain Forest in Olympic National Park on the western flank of the Olympic Mountains receives an annual erage precipitation of 142 in (3,600 mm). Sixty miles (97 km) to the south of Seattle, the state capital Olympia, which is out of the Olympic Mountains' rain shadow, receives an annual erage precipitation of 50 in (1,270 mm).[13] The city of Bremerton, about 15 mi (24 km) west of downtown Seattle on the other side of the Puget Sound, receives 56.4 in (1,430 mm) of precipitation annually.[13]
One of many exceptions to Seattle's reputation as a damp location occurs in El Niño years, when marine weather systems track as far south as California and less than the usual precipitation falls in the Puget Sound area.[23] However, the El Nino of 2015-2016 caused an increase in rainfall. Since the region's water comes from mountain snow packs during the dry summer months, El Niño winters can not only produce substandard skiing but can result in water rationing and a shortage of hydroelectric power the following summer.[24]
Averages[edit] vteClimate data for Seattle (SeaTac International Airport), 1991–2020 normals Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Average precipitation inches (mm) 5.78(147) 3.76(96) 4.17(106) 3.18(81) 1.88(48) 1.45(37) 0.60(15) 0.97(25) 1.61(41) 3.91(99) 6.31(160) 5.72(145) 39.34(999) Average snowfall inches (cm) 2.5(6.4) 2.2(5.6) 0.9(2.3) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0.5(1.3) 2.1(5.3) 8.2(20.9) Average precipitation days (≥ 0.01 in) 18.7 15.9 17.1 15.0 11.3 9.2 4.7 4.9 8.3 14.3 18.4 18.4 156.2 Average snowy days (≥ 0.1 in) 2.3 2.0 0.9 0 0 0 0 0 0 0 0.2 1.5 4.7 Source: NOAA[13] Rainfall Extremes[edit] Lowest[edit] Period Record rainfall Year Year 19.85 inches (504 mm) 1944 Spring (March–May) 2.23 inches (57 mm) 1924 Summer (June–August) 0.65 inches (17 mm) 1919 Autumn (September–November) 2.32 inches (59 mm) 1929 Winter (December–February) 5.21 inches (132 mm) 1976–1977 January 0.58 inches (15 mm) 1985 February 0.34 inches (8.6 mm) 1920 March 0.42 inches (11 mm) 1924 April 0.16 inches (4.1 mm) 1939 May 0.12 inches (3.0 mm) 1992, 2018 June 0.03 inches (0.76 mm) 1922 July 0.00 inches (0 mm) 1896, 1922, 2017 August Trace 2012 September Trace 1975, 1991 October 0.02 inches (0.51 mm) 1895 November 0.74 inches (19 mm) 1976 December 1.00 inch (25 mm) 1944 Highest[edit] Period Record rainfall Year Year 55.14 inches (1,401 mm) 1950 Spring (March–May) 16.77 inches (426 mm) 2014 Summer (June–August) 8.43 inches (214 mm) 1968 Autumn (September–November) 18.61 inches (473 mm) 2006 Winter (December–February) 24.63 inches (626 mm) 2015–2016 January 12.92 inches (328 mm) 1953 February 9.11 inches (231 mm) 1961 March 9.44 inches (240 mm) 2014 April 6.53 inches (166 mm) 1991 May 4.76 inches (121 mm) 1948 June 3.90 inches (99 mm) 1946 July 2.39 inches (61 mm) 1983 August 4.59 inches (117 mm) 1975 September 6.17 inches (157 mm) 2013 October 10.05 inches (255 mm) 2016 November 15.63 inches (397 mm) 2006 December 15.33 inches (389 mm) 1933Snowfall[edit] Highest[edit] Period Record most snowfall Year Year[a] 63.6 in (162 cm) 1916 Seasonal (July–June) 67.5 in (171 cm) 1968–1969 Spring (March–May) 18.2 in (46 cm) 1951 Autumn (September–November) 20.5 in (52 cm) 1896 Winter (December–February) 58.7 in (149 cm) 1915–1916 January 57.2 in (145 cm) 1950 February 35.4 in (90 cm) 1916 March 18.2 in (46 cm) 1951 April 2.4 in (6.1 cm) 1920 May Trace 1993, 1990, 1989, 1974, 1965, 1955, 1953, 1951, 1925 June–September 0 in (0 cm) – October 2.0 in (5.1 cm) 1971 November 20.5 in (52 cm) 1896 December 22.1 in (56 cm) 1968 Other phenomena[edit] Downtown Seattle erages 71 completely sunny days a year, with most of those days occurring between May and September[25] Sunshine, UV and daylight[edit]
The city generally experiences cloudy conditions, with clear days occurring infrequently. As a result of the city's latitude, it experiences a moderate difference in daylight hours between summer and winter, though is not subject to the extremes of cities further north.[26] The Seattle area is the cloudiest region of the United States, due in part to frequent storms and lows moving in from the adjacent Pacific Ocean. Seattle is cloudy 201 days out of the year and partly cloudy 93 days.[25] (Official weather and climatic data is collected at Seattle–Tacoma International Airport, located about 19 km (12 mi) south of downtown in the city of SeaTac, which is at a higher elevation, and records more cloudy days and fewer partly cloudy days per year.[25])
Climate data for Seattle Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Mean monthly sunshine hours 69.8 108.8 178.4 207.3 253.7 268.4 312.0 281.4 221.7 142.6 72.7 52.9 2,169.7 Mean daily daylight hours 9.0 10.3 12.0 13.7 15.2 15.9 15.5 14.2 12.5 10.8 9.3 8.5 12.2 Percentage possible sunshine 25 38 48 51 54 56 65 64 59 42 26 20 49 Average ultriolet index 1 2 3 5 6 7 7 6 5 3 1 1 4 Source 1: NOAA (relative humidity and sun 1961–1990)[27] Source 2: Weather Atlas[26] Wind[edit]The Puget Sound Convergence Zone is an important feature of Seattle's weather. In the convergence zone, air arriving from the north meets air flowing in from the south. Both streams of air originate over the Pacific Ocean; airflow is split by the Olympic Mountains to Seattle's west, then reunited to the east. When the air currents meet, they are forced upward, resulting in convection.[28] Thunderstorms caused by this activity are usually weak and can occur north and south of town, but Seattle itself rarely receives more than occasional thunder and small hail showers. The Hanukkah Eve Wind Storm in December 2006 is an exception that brought hey rain and winds gusting up to 69 mph (111 km/h), an event that was not caused by the Puget Sound Convergence Zone and was widespread across the Pacific Northwest. In December 2007, a strong windstorm brought hurricane force winds and hey rain, leading to 5 deaths.[29][30]
Climate change[edit]Being a coastal city, Seattle may experience significant effects from rising sea levels. The sea has risen by 6 inches (15 cm) in the past century, and is expected to rise 28 inches (71 cm) by 2100 and 47 inches (120 cm) by 2150. It is expected that by this time, frequent flooding will become a problem, with now-annual extreme king tide's becoming monthly or even daily events.[31]
Temperature[edit]The temperature in Seattle has generally increased steadily and this trend is expected to continue due to anthropogenic warming. For the last century, the erage has increased roughly 0.3 degrees Fahrenheit each decade. By the end of the century, it is predicted that there will be on erage around two weeks of 90 °F (32 °C) days each year.[31]
Homes in the area he historically not used air conditioning due to the temperate summer climate; the United States Census Bureau found that 31 percent of households in the Seattle metropolitan area used air conditioning. Several major heat wes in the 2010s and 2020s, including the June 2021 heat dome that set record temperatures in the state, led to a large increase in air conditioning use.[32] By the end of 2021, the Census Bureau's biannual housing survey found that 53 percent of households in the metropolitan area had air conditioning.[33]
Precipitation[edit]Precipitation in the city has increased slightly, but this trend is expected to continue. Extreme rainfall events he become more frequent over the previous years and this trend is also expected to continue.[31]
Station data[edit] This article needs to be updated. The reason given is: Some of this data is more than five years old; parts are more than 10 years old. Please help update this article to reflect recent events or newly ailable information. (November 2024) vteClimate data for Seattle (SeaTac Airport), 1991–2020 normals,[b] extremes 1894–present[c] Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Record high °F (°C) 67(19) 70(21) 79(26) 89(32) 93(34) 108(42) 103(39) 99(37) 98(37) 89(32) 74(23) 66(19) 108(42) Mean maximum °F (°C) 57.0(13.9) 59.1(15.1) 66.4(19.1) 74.3(23.5) 81.9(27.7) 85.8(29.9) 91.2(32.9) 89.9(32.2) 84.1(28.9) 72.0(22.2) 61.6(16.4) 56.8(13.8) 94.1(34.5) Mean daily maximum °F (°C) 48.0(8.9) 50.3(10.2) 54.2(12.3) 59.3(15.2) 66.3(19.1) 71.1(21.7) 77.4(25.2) 77.6(25.3) 71.6(22.0) 60.5(15.8) 52.1(11.2) 47.0(8.3) 61.3(16.3) Daily mean °F (°C) 42.8(6.0) 44.0(6.7) 47.1(8.4) 51.3(10.7) 57.5(14.2) 62.0(16.7) 67.1(19.5) 67.4(19.7) 62.6(17.0) 53.8(12.1) 46.5(8.1) 42.0(5.6) 53.7(12.1) Mean daily minimum °F (°C) 37.7(3.2) 37.7(3.2) 39.9(4.4) 43.3(6.3) 48.7(9.3) 53.0(11.7) 56.8(13.8) 57.2(14.0) 53.6(12.0) 47.0(8.3) 40.9(4.9) 37.1(2.8) 46.1(7.8) Mean minimum °F (°C) 26.1(−3.3) 27.3(−2.6) 31.3(−0.4) 35.6(2.0) 40.6(4.8) 46.6(8.1) 51.5(10.8) 51.7(10.9) 45.8(7.7) 36.8(2.7) 29.2(−1.6) 25.4(−3.7) 21.5(−5.8) Record low °F (°C) 0(−18) 1(−17) 11(−12) 29(−2) 28(−2) 38(3) 43(6) 44(7) 35(2) 28(−2) 6(−14) 6(−14) 0(−18) Average precipitation inches (mm) 5.78(147) 3.76(96) 4.17(106) 3.18(81) 1.88(48) 1.45(37) 0.60(15) 0.97(25) 1.61(41) 3.91(99) 6.31(160) 5.72(145) 39.34(999) Average snowfall inches (cm) 1.8(4.6) 2.2(5.6) 0.4(1.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.0(0.0) 0.2(0.51) 1.7(4.3) 6.3(16) Average precipitation days (≥ 0.01 in) 18.7 15.9 17.1 15.0 11.3 9.2 4.7 4.9 8.3 14.3 18.4 18.4 156.2 Average snowy days (≥ 0.1 in) 1.4 1.2 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.5 4.7 Average relative humidity (%) 78.0 75.2 73.6 71.4 68.9 67.1 65.4 68.2 73.2 78.6 79.8 80.1 73.3 Average dew point °F (°C) 33.1(0.6) 35.1(1.7) 36.3(2.4) 38.8(3.8) 43.5(6.4) 48.2(9.0) 51.4(10.8) 52.7(11.5) 50.2(10.1) 45.1(7.3) 38.8(3.8) 34.3(1.3) 42.3(5.7) Mean monthly sunshine hours 69.8 108.8 178.4 207.3 253.7 268.4 312.0 281.4 221.7 142.6 72.7 52.9 2,169.7 Percentage possible sunshine 25 38 48 51 54 56 65 64 59 42 26 20 49 Average ultriolet index 1 2 3 5 6 7 7 6 5 3 1 1 4 Source 1: NOAA (relative humidity, dew point and sun 1961–1990)[34][35][36] Source 2: Weather Atlas (UV)[37] This graph was using the legacy Graph extension, which is no longer supported. It needs to be converted to the new Chart extension.See or edit raw graph data.
Explanatory notes[edit] ^ Some traces of snowfall actually he been may hail, thus entries of trace amounts in summer months he been excluded. ^ Mean monthly maxima and minima (i.e. the highest and lowest temperature readings during an entire month or year) calculated based on data at said location from 1991 to 2020. ^ Official records are restricted to SeaTac Airport from January 1945 onward.[34] References[edit] ^ "U.S. Climate Data". ^ "Seattle the next Saint-Tropez? Not quite, but Mediterranean climate trends continue". Q13 FOX News. June 8, 2018. Retrieved December 1, 2018. ^ "Seattle, Washington Köppen Climate Classification (Weatherbase)". Weatherbase. Retrieved November 4, 2018. ^ Bloom, Jessi; Boehnlein, De (February 4, 2016). Practical Permaculture: for Home Landscapes, Your Community, and the Whole Earth. Timber Press. ISBN 9781604697421. ^ Climatology. Jones & Bartlett Publishers. 1942. p. 207. ISBN 978-1-284-05427-9. {{cite book}}: ISBN / Date incompatibility (help) ^ "Seattle - WA" (PDF). South Seattle College. Archived from the original (PDF) on November 4, 2018. ^ Kottek, M.; J. Grieser; C. Beck; B. Rudolf; F. Rubel (2006). "World Map of the Köppen-Geiger climate classification updated". Meteorol. Z. 15 (3): 259–263. Bibcode:2006MetZe..15..259K. doi:10.1127/0941-2948/2006/0130. Retrieved February 15, 2007. ^ "3 Concept and classification". Global ecological zoning for the global forest resources assessment 2000. Rome: UN Food and Agriculture Organization. Forestry Department. 2001. Retrieved December 30, 2011. ^ Dale D. Goble; Paul W. Hirt (March 15, 2012). Northwest Lands, Northwest Peoples: Readings in Environmental History. University of Washington Press. pp. 58–59. ISBN 978-0-295-80137-7. ^ "USDA Plant Hardiness Zone Map". United States Department of Agriculture. Archived from the original on November 21, 2023. Retrieved November 21, 2023. ^ a b Conner, Glen. 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