Climate of Seattle

Seattle
Climate chart (explanation)
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5.2
 
 
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38
 
 
3.9
 
 
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2
 
 
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1.5
 
 
66
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0.8
 
 
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1.7
 
 
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█ Average max. and min. temperatures in °F
█ Precipitation totals in inches
Source: [1]
Metric conversion
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132
 
 
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99
 
 
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42
 
 
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99
 
 
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160
 
 
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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 heavy snowfall is uncommon.

  1. ^ "U.S. Climate Data".
  2. ^ "Seattle the next Saint-Tropez? Not quite, but Mediterranean climate trends continue". Q13 FOX News. June 8, 2018. Retrieved December 1, 2018.
  3. ^ "Seattle, Washington Köppen Climate Classification (Weatherbase)". Weatherbase. Retrieved November 4, 2018.
  4. ^ Bloom, Jessi; Boehnlein, Dave (February 4, 2016). Practical Permaculture: for Home Landscapes, Your Community, and the Whole Earth. Timber Press. ISBN 9781604697421.
  5. ^ Climatology. Jones & Bartlett Publishers. 1942. p. 207. ISBN 978-1-284-05427-9.
  6. ^ "Seattle - WA" (PDF). South Seattle College. Archived from the original (PDF) on November 4, 2018.
  7. ^ 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.
  8. ^ "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.
  9. ^ 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.
  10. ^ "USDA Plant Hardiness Zone Map". United States Department of Agriculture. Archived from the original on November 21, 2023. Retrieved November 21, 2023.
  11. ^ Conner, Glen. "History of Weather Observations, Seattle Washington 1870-1948" (PDF). Purdue University. Archived from the original (PDF) on 2023-09-11. Retrieved 27 May 2023.
  12. ^ "Monthly Averages for Seattle, WA". The Weather Channel. Archived from the original on July 10, 2014. Retrieved September 28, 2007.
  13. ^ Cite error: The named reference NOWData1 was invoked but never defined (see the help page).
  14. ^ Office of the Washington State Climatologist. "July 2009 Heat Wave". University of Washington. Retrieved 2 June 2023.
  15. ^ "Seattle Weather and Climate". Archived from the original on September 26, 2007. Retrieved September 28, 2007.
  16. ^ Sperling, Bert; Peter Sander (2007). Cities Ranked and Rated. Wiley. ISBN 978-0-470-06864-9.