Английская Википедия:Climate of Seattle

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Файл:SIFF rainy line 01.jpg

Rainy day in Capitol Hill, Seattle. Seattle experiences around 150 days with at least Шаблон:Convert 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) although some sources put the city in the oceanic zone (Trewartha: Do). It has cool, wet winters and warm, dry summers, covering characteristics of both. 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). The city is part of USDA hardiness zone 9a, with surrounding pockets falling under 8b.

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. The hottest officially recorded temperature was Шаблон:Convert on June 28, 2021; the coldest recorded temperature was Шаблон:Convert on January 31, 1950; the record cold daily maximum is Шаблон:Convert on January 14, 1950, while, conversely, the record warm daily minimum is Шаблон:Convert on June 27, 2021.

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), 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, as the city reports thunder on just seven days per year. Similarly, the city typically receives at least light snowfall every year, though heavy snowfall is uncommon.

Temperature

Файл:Climatological Data for SEATTLE TACOMA AIRPORT, WA - June 2021.pdf

Weather report from Seattle-Tacoma Airport in June 2021. Seattle recorded its highest temperature ever on June 28, reaching Шаблон:Convert.

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 heatwaves are rare, as are cold temperatures. Hot temperature extremes are enhanced by dry, compressed wind from the west slopes of the Cascades, while cold temperatures are generated mainly from the Fraser Valley in British Columbia. Records are taken from the Seattle City area from 1894 to 1944 and at Sea-Tac Airport from 1945.

Averages

In an average year, the temperature will usually be between Шаблон:Convert and Шаблон:Convert with temperatures greatly exceeding these values being uncommon. Temperatures above Шаблон:Convert and below Шаблон:Convert are very rare, with the last occurrences being June 28, 2021 and November 24, 2010, respectively.

Highest daily temperatures

Period	Record temperature	Date
Шаблон:Date table sorting	Шаблон:Convert	Jan 28, 1931
Шаблон:Date table sorting	Шаблон:Convert	Feb 27, 1968
Шаблон:Date table sorting	Шаблон:Convert	Mar 20, 2019 Mar 19, 2019
Шаблон:Date table sorting	Шаблон:Convert	Apr 18, 2016
Шаблон:Date table sorting	Шаблон:Convert	May 21, 1963
Шаблон:Date table sorting	Шаблон:Convert	Jun 28, 2021
Шаблон:Date table sorting	Шаблон:Convert	Jul 29, 2009
Шаблон:Date table sorting	Шаблон:Convert	Aug 9, 1981 Aug 9, 1960
Шаблон:Date table sorting	Шаблон:Convert	Sep 2, 1988
Шаблон:Date table sorting	Шаблон:Convert	Oct 1, 1987
Шаблон:Date table sorting	Шаблон:Convert	Nov 3, 2010 Nov 4, 1949
Шаблон:Date table sorting	Шаблон:Convert	Dec 10, 2014

Lowest daily temperatures

Period	Record temperature	Date
Шаблон:Date table sorting	Шаблон:Convert	Jan 31, 1950
Шаблон:Date table sorting	Шаблон:Convert	Feb 1, 1950
Шаблон:Date table sorting	Шаблон:Convert	Mar 4, 1955
Шаблон:Date table sorting	Шаблон:Convert	Apr 5, 1975 Apr 1, 1953 Apr 7–8, 1952 Apr 21, 1951
Шаблон:Date table sorting	Шаблон:Convert	May 1, 1954
Шаблон:Date table sorting	Шаблон:Convert	Jun 12, 1952
Шаблон:Date table sorting	Шаблон:Convert	Jul 4, 1949 Jul 24, 1953 Jul 2, 1954
Шаблон:Date table sorting	Шаблон:Convert	Aug 13–14, 1955 Aug 27, 1952 Aug 29, 1951 Aug 4, 1950 Aug 21, 1947
Шаблон:Date table sorting	Шаблон:Convert	Sep 27, 1972
Шаблон:Date table sorting	Шаблон:Convert	Oct 19, 1949
Шаблон:Date table sorting	Шаблон:Convert	Nov 15, 1955
Шаблон:Date table sorting	Шаблон:Convert	Dec 30, 1968

Highest averages

Period	Record mean	Year
Year	Шаблон:Convert	1940, 2015
Spring (March–May)	Шаблон:Convert	1934
Summer (June–August)	Шаблон:Convert	2015
Autumn (September–November)	Шаблон:Convert	1967
Winter (December–February)	Шаблон:Convert	1940–1941
January	Шаблон:Convert	2010
February	Шаблон:Convert	2015
March	Шаблон:Convert	1941
April	Шаблон:Convert	2016
May	Шаблон:Convert	2018
June	Шаблон:Convert	2015
July	Шаблон:Convert	2015
August	Шаблон:Convert	1967
September	Шаблон:Convert	1967
October	Шаблон:Convert	2014
November	Шаблон:Convert	1899
December	Шаблон:Convert	1939

Lowest averages

Period	Record mean	Year
Year	Шаблон:Convert	1955
Spring (March–May)	Шаблон:Convert	1955
Summer (June–August)	Шаблон:Convert	1954
Autumn (September–November)	Шаблон:Convert	1985
Winter (December–February)	Шаблон:Convert	1949–1950, 1948–1949
January	Шаблон:Convert	1950
February	Шаблон:Convert	1956
March	Шаблон:Convert	1955
April	Шаблон:Convert	1955
May	Шаблон:Convert	1962
June	Шаблон:Convert	1953
July	Шаблон:Convert	1955
August	Шаблон:Convert	1910
September	Шаблон:Convert	1972
October	Шаблон:Convert	1946
November	Шаблон:Convert	1985
December	Шаблон:Convert	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. To distinguish these older numbers we mark them below in italics.

Precipitation

Файл:Cherry St after the big snowfall of 1880, looking northeast, Seattle, January 10, 1880 (PEISER 144).jpeg

Cherry Street after heavy snowfall on January 10, 1880

The 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. In an average year, at least Шаблон:Convert of precipitation falls on 150 days, more than nearly all U.S. cities east of the Rocky Mountains. In November, Seattle averages 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. 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 heaviest 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. For instance, on average, less than Шаблон:Convert of rain falls in July and August combined when rain is less common.

Annually, total precipitation averages Шаблон:Convert, 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 Шаблон:Convert, fell between June 18 and August 13, 2017. The city also sees snow, primarily in winter, but sometimes in the late autumn and early spring. Snowfall averages Шаблон:Convert per year but is highly variable between winter seasons. The most rainfall in 24 hours was Шаблон:Convert on October 20, 2003, and the most snowfall was Шаблон:Convert on February 2, 1916. Seattle typically receives some snowfall on an annual basis but heavy snow is rare. Average annual snowfall, as measured at Sea-Tac Airport, is Шаблон:Convert. 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 Шаблон:Convert to the west, the Hoh Rain Forest in Olympic National Park on the western flank of the Olympic Mountains receives an annual average precipitation of Шаблон:Convert. Шаблон:Convert to the south of Seattle, the state capital Olympia, which is out of the Olympic Mountains' rain shadow, receives an annual average precipitation of Шаблон:Convert. The city of Bremerton, about Шаблон:Convert west of downtown Seattle on the other side of the Puget Sound, receives Шаблон:Convert of precipitation annually.

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. 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.

Rainfall Extremes

Lowest

Period	Record rainfall	Year
Year	Шаблон:Convert	1944
Spring (March–May)	Шаблон:Convert	1924
Summer (June–August)	Шаблон:Convert	1919
Autumn (September–November)	Шаблон:Convert	1929
Winter (December–February)	Шаблон:Convert	1976–1977
January	Шаблон:Convert	1985
February	Шаблон:Convert	1920
March	Шаблон:Convert	1924
April	Шаблон:Convert	1939
May	Шаблон:Convert	1992, 2018
June	Шаблон:Convert	1922
July	Шаблон:Convert	1896, 1922, 2017
August	Trace	2012
September	Trace	1975, 1991
October	Шаблон:Convert	1895
November	Шаблон:Convert	1976
December	Шаблон:Convert	1944

Highest

Period	Record rainfall	Year
Year	Шаблон:Convert	1950
Spring (March–May)	Шаблон:Convert	2014
Summer (June–August)	Шаблон:Convert	1968
Autumn (September–November)	Шаблон:Convert	2006
Winter (December–February)	Шаблон:Convert	2015–2016
January	Шаблон:Convert	1953
February	Шаблон:Convert	1961
March	Шаблон:Convert	2014
April	Шаблон:Convert	1991
May	Шаблон:Convert	1948
June	Шаблон:Convert	1946
July	Шаблон:Convert	1983
August	Шаблон:Convert	1975
September	Шаблон:Convert	2013
October	Шаблон:Convert	2016
November	Шаблон:Convert	2006
December	Шаблон:Convert	1933

Snowfall

Highest

Period	Record most snowfall	Year
YearШаблон:Efn	Шаблон:Convert	1916
Seasonal (July–June)	Шаблон:Convert	1968–1969
Spring (March–May)	Шаблон:Convert	1951
Autumn (September–November)	Шаблон:Convert	1896
Winter (December–February)	Шаблон:Convert	1915–1916
January	Шаблон:Convert	1950
February	Шаблон:Convert	1916
March	Шаблон:Convert	1951
April	Шаблон:Convert	1920
May	Trace	1993, 1990, 1989, 1974, 1965, 1955, 1953, 1951, 1925
June–September	Шаблон:Convert	–
October	Шаблон:Convert	1971
November	Шаблон:Convert	1896
December	Шаблон:Convert	1968

Other phenomena

Vew of the downtown Seattle skyline, on the waterfront, with the Seattle Aquarium on the left and Seattle Great Wheel on the right.

Downtown Seattle averages 71 completely sunny days a year, with most of those days occurring between May and September

Sunshine, UV and daylight

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. 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. (Official weather and climatic data is collected at Seattle–Tacoma International Airport, located about Шаблон:Convert 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.)

Wind

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. 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 heavy rain and winds gusting up to Шаблон:Convert, 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 heavy rain, leading to 5 deaths.

Climate change

Being a coastal city, Seattle may experience significant effects from rising sea levels. The sea has risen by Шаблон:Convert in the past century, and is expected to rise Шаблон:Convert by 2100 and Шаблон:Convert 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.

Temperature

The temperature in Seattle has generally increased steadily and this trend is expected to continue due to anthropogenic warming. For the last century, the average has increased roughly 0.3 degrees Fahrenheit each decade. By the end of the century, it is predicted that there will be on average around two weeks of Шаблон:Convert days each year.

Precipitation

Precipitation in the city has increased slightly, but this trend is expected to continue. Extreme rainfall events have become more frequent over the previous years and this trend is also expected to continue.