Editing San Francisco (section)

===Climate===
[[File:San francisco in fog with rays.jpg|thumb|upright=0.8|left|[[San Francisco fog]] is a regular phenomenon in the summer.]]
San Francisco has a [[warm-summer Mediterranean climate]] ([[Köppen climate classification|Köppen]]: ''Csb'', [[Trewartha climate classification|Trewartha]]: Csll), characteristic of California's coast, with moist winters and dry summers.<ref>[http://ggweather.com/sf/narrative.html Climate of San Francisco: Narrative Description] Golden Gate Weather Services. Retrieved September 5, 2006.</ref> San Francisco's weather is strongly influenced by the [[California Current|cool currents]] of the Pacific Ocean on the west side of the city, and the water of [[San Francisco Bay]] to the north and east. This moderates temperature swings and produces a remarkably mild year-round climate with little seasonal temperature variation.<ref>{{Cite web|title=San Francisco climate: Average Temperature, weather by month, San Francisco water temperature - Climate-Data.org|url=https://en.climate-data.org/north-america/united-states-of-america/california/san-francisco-385/|access-date=August 5, 2021|website=en.climate-data.org}}</ref>

Among major U.S. cities, San Francisco has the coolest daily mean, maximum, and minimum temperatures for June, July, and August.<ref>{{cite web|title=Coolest US Cities in Summer|url=http://www.currentresults.com/Weather-Extremes/US/coldest-cities-summer.php|last1=Osborn|first1=Liz|work=Weather Extremes|publisher=Current Results Nexus|access-date=July 25, 2010|archive-url=https://web.archive.org/web/20100724192713/http://www.currentresults.com/Weather-Extremes/US/coldest-cities-summer.php |archive-date = July 24, 2010|url-status=live}}</ref> During the summer, rising hot air in California's interior valleys creates a low-pressure area that draws winds from the [[North Pacific High]] through the [[Golden Gate]], which creates the city's [[San Francisco fog|characteristic cool winds and fog]].<ref>{{Cite journal|last=Gilliam|first=Harold|author-link=Harold Gilliam|title=Cutting Through the Fog: Demystifying the Summer Spectacle|journal=Bay Nature|date=July–September 2002|url=http://baynature.org/articles/jul-sep-2002/cutting-through-the-fog}}</ref> The fog is less pronounced in eastern neighborhoods and during the late summer and early fall. The year's warmest month, on average, is September, and on average, October is warmer than July, especially in daytime.

Temperatures reach or exceed {{convert|80|°F|abbr=on}} on an average of only 21 and 23&nbsp;days a year at downtown and [[San Francisco International Airport]] (SFO), respectively.<ref name="San Francisco NOAA"/> The dry period of May to October is mild to warm, with the normal monthly mean temperature peaking in September at {{convert|62.7|°F|abbr=on}}.<ref name="San Francisco NOAA"/> The rainy period of November to April is slightly cooler, with the normal monthly mean temperature reaching its lowest in January at {{convert|51.3|°F|abbr=on}}.<ref name="San Francisco NOAA"/> On average, there are 73 rainy days a year, and annual precipitation averages {{convert|23.65|in|mm|0}}.<ref name="San Francisco NOAA"/> Variation in precipitation from year to year is high. Above-average rain years are often associated with warm [[El Niño]] conditions in the Pacific while dry years often occur in cold water [[La Niña]] periods. In 2013 (a "La Niña" year), a record low {{convert|5.59|in|mm|abbr=on}} of rainfall was recorded at downtown San Francisco, where records have been kept since 1849.<ref name="San Francisco NOAA"/> Snowfall in the city is very rare, with only 10 measurable accumulations recorded since 1852, most recently in 1976 when up to {{convert|5|in|cm}} fell on Twin Peaks.<ref>[http://ggweather.com/sf/snow.html Climate of San Francisco: Snowfall] Golden Gate Weather Services. Retrieved December 3, 2006.</ref><ref>{{cite news|url = http://blog.sfgate.com/thebigevent/2012/11/29/blizzard-of-awesome-the-san-francisco-snowfall-of-1976/|title = Blizzard of awesome: The San Francisco snowfall of 1976|first1 = Peter|last1=Hartlaub|work = San Francisco Chronicle|date = November 29, 2012|access-date = February 1, 2013}}</ref>
[[File:View from Mirounga Bay.jpg|thumb|right|The [[Farallon Islands]] are located in the [[Gulf of the Farallones]], off the [[West Coast of the United States|Pacific coast]] of San Francisco.]]
The highest recorded temperature at the official [[National Weather Service]] downtown observation station{{efn|Station currently at the [[San Francisco Mint#Current building|United States Mint]] building<ref>{{cite web |url=https://hoodline.com/2014/05/secretly-awesome-the-lower-haight-weather-station/|title=Secretly Awesome: The Lower Haight Weather Station|author=Dudley, Andrew|date=May 1, 2014|website=hoodline}}</ref>{{self-published inline|date=February 2021}} }} was {{convert|106|F|C}} on September 1, 2017.<ref>{{cite news |last1=Ruberstein |first1=Steve |last2=Asimov |first2=Nanette |last3=Lyons |first3=Jenna |title=San Francisco hits 106 degrees – shatters all-time record |url=http://www.sfgate.com/bayarea/article/Hey-San-Francisco-get-ready-for-the-heat-12166706.php |date=September 1, 2017 |newspaper=San Francisco Chronicle |access-date=September 2, 2017}}</ref> During that hot spell, the warmest ever night of {{convert|71|F|C}} was also recorded.<ref name="San Francisco NOAA2">{{cite web|url=https://www.weather.gov/wrh/Climate?wfo=mtr|title=NOWData for San Francisco, CA forecast office|publisher=[[NOAA]]|access-date=July 26, 2022}}</ref> The lowest recorded temperature was {{convert|27|F|C}} on December 11, 1932.<ref>{{cite web|url = http://www.wrcc.dri.edu/cgi-bin/cliGCStT.pl?ca7772|title = San Fran Mission Dolore, California (047772) Period of Record General Climate Summary – Temperature|work=Western Regional Climate Center|publisher=[[Desert Research Institute]]|year = 2010|access-date =July 25, 2010|archive-url = https://web.archive.org/web/20110513121708/http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca7772 |archive-date = May 13, 2011|url-status=live}} ([http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca7772 Main page])</ref>

During an average year between 1991 and 2020, San Francisco recorded a warmest night at {{convert|64|F|C}} and a coldest day at {{convert|49|F|C}}.<ref name="San Francisco NOAA"/> The coldest daytime high since the station's opening in 1945 was recorded in December 1972 at {{convert|37|F|C}}.<ref name="San Francisco NOAA"/>

As a coastal city, San Francisco will be heavily affected by [[climate change]]. {{as of|2021}}, sea levels are projected to rise by as much as {{convert|5|ft}}, resulting in periodic flooding, rising groundwater levels, and lowland floods from more severe storms.<ref>{{cite news |last1=Tuma |first1=Drew |last2=Didion |first2=Tim |title=UN climate report puts focus on sea level rise threat to San Francisco Bay |url=https://abc7news.com/un-climate-report-bay-area-rising-sea-level-change-ocean/10941431/ |access-date=January 31, 2022 |work=ABC7 San Francisco |date=August 10, 2021}}</ref>

San Francisco falls under the [[USDA]] 10b Plant [[hardiness zone]], though some areas, particularly downtown, border zone 11a.<ref>{{cite web|title=USDA Plant Hardiness Zone Map|url=http://planthardiness.ars.usda.gov/PHZMWeb/#|author=Agricultural Research Center, PRISM Climate Group Oregon State University|work=USDA|access-date=February 24, 2014|url-status=dead|archive-url=https://web.archive.org/web/20140227032333/http://planthardiness.ars.usda.gov/PHZMWeb/|archive-date=February 27, 2014}}</ref><ref>{{cite web|url=http://www.plantmaps.com/interactive-california-usda-plant-zone-hardiness-map.php|title=California Interactive USDA Plant Hardiness Zone Map|access-date=December 19, 2016}}</ref>

{{San Francisco weatherbox}}