San Diego

===Climate===
{{Main|Climate of San Diego}}
{{climate chart
| San Diego
|50.3|66.4|1.98
|51.8|66.2|2.20
|54.5|67.0|1.46
|57.1|68.8|0.65
|60.0|69.5|0.28
|62.6|71.7|0.05
|66.1|75.3|0.08
|67.5|77.3|0.01
|66.2|77.2|0.12
|61.5|74.6|0.50
|54.8|70.7|0.79
|49.8|66.0|1.67
|float     = left
|clear     = left
|units     = imperial
|source    = [[National Oceanic and Atmospheric Administration|NOAA]]<ref>{{Cite web|url=https://www.ncei.noaa.gov/access/us-climate-normals/|title = NOAA NCEI U.S. Climate Normals Quick Access}}</ref>
}}

Under the [[Köppen–Geiger climate classification system]], the San Diego area has been variously categorized as having either a [[hot semi-arid climate]] (''[[hot semi-arid climate|BSh]]'' in the original classification<ref>{{cite journal|author=M. Kottek|author2=J. Grieser |author3=C. Beck |author4=B. Rudolf |author5=F. Rubel|title=World Map of the Köppen-Geiger climate classification updated|journal=Meteorol. Z.|volume=15|issue=3|pages=259–263|url=https://opus.bibliothek.uni-augsburg.de/opus4/files/40083/metz_Vol_15_No_3_p259-263_World_Map_of_the_Koppen_Geiger_climate_classification_updated_55034.pdf|doi=10.1127/0941-2948/2006/0130|bibcode=2006MetZe..15..259K|access-date=July 9, 2013|year=2006|url-access=|url-status=|archive-url=|archive-date=}}</ref> and ''BSkn'' in modified Köppen classification with the n denoting summer fog)<ref>{{Cite web|url=http://www.dfg.ca.gov/biogeodata/atlas/pdf/Clim_12b_web.pdf|archive-url=https://web.archive.org/web/20100331081841/http://www.dfg.ca.gov/biogeodata/atlas/pdf/Clim_12b_web.pdf|archive-date=March 31, 2010|title=Atlas of the Biodiversity of California|date=March 31, 2010|access-date=August 7, 2018}}</ref> or a [[hot-summer Mediterranean climate]]<ref>Francisco Pugnaire and Fernando Valladares eds. [https://books.google.com/books?id=Fqc-_Zv3jIMC&dq=%22san+diego%22+%22mediterranean%22+koppen&pg=PA287 Functional Plant Ecology]. 2d ed. 2007. p.287.</ref> (''Csa'').<ref>Michael Allaby, Martyn Bramwell, Jamie Stokes, eds. [https://books.google.com/books?id=iHPbFExmzoQC&dq=%22san+diego%22+%22mediterranean%22+koppen&pg=PA182 Weather and Climate: An Illustrated Guide to Science]. 2006. p.182.</ref> San Diego's climate is characterized by warm, dry summers and mild winters, with most of the annual precipitation falling between December and March. The city has a mild climate year-round,<ref>Michalski, Greg et al. [http://www.cee.mtu.edu/~reh/papers/pubs/non_Honrath/michalski03_GL017015.pdf First Measurements and Modeling of ∆<sup>17</sup>O in atmospheric nitrate] {{webarchive|url=https://web.archive.org/web/20130724021112/http://www.cee.mtu.edu/~reh/papers/pubs/non_Honrath/michalski03_GL017015.pdf |date=July 24, 2013 }}. Geophysical Research Letters, Vol. 30, No. 16. p.3. 2003.</ref> with an average of 201 days above {{convert|70|°F|°C|abbr=on}} and low rainfall ({{convert|9|-|13|in|mm|disp=x| [|]}} annually).<!--<ref name = "NOAA">{{cite web|url=http://www.wrh.noaa.gov/sgx/climate/san-san-month.htm |title=National Oceanic and Atmospheric Agency: San Diego climate by month |publisher=Wrh.noaa.gov |access-date=May 4, 2011}}</ref>-->

The climate in San Diego, like most of Southern California, often varies significantly over short geographical distances, resulting in [[microclimate]]s. In San Diego, this is mostly because of the city's topography (the Bay, and the numerous hills, mountains, and canyons). Frequently, particularly during the "May gray/[[June Gloom|June gloom]]" period, a thick "[[marine layer]]" cloud cover keeps the air cool and damp within a few miles of the coast, but yields to bright cloudless sunshine approximately {{convert|5|–|10|mi|km|0}} inland.<ref>{{cite web |url=http://meteora.ucsd.edu/cap/gloom.html |title=UCSD |publisher=Meteora.ucsd.edu |date=May 14, 2010 |access-date=July 1, 2010 |archive-url=https://web.archive.org/web/20100613050427/http://meteora.ucsd.edu/cap/gloom.html |archive-date=June 13, 2010 }}</ref> Sometimes the June gloom lasts into July, causing cloudy skies over most of San Diego for the entire day.<ref name=weather1>{{cite web|url=http://www.weather.com/outlook/travel/businesstraveler/wxclimatology/monthly/USca0982|title=Monthly Averages for San Diego, CA|access-date=April 22, 2009|publisher=[[The Weather Channel (United States)|The Weather Channel]]|archive-url=https://web.archive.org/web/20090502201247/http://www.weather.com/outlook/travel/businesstraveler/wxclimatology/monthly/USCA0982|archive-date=May 2, 2009}}</ref><ref name=weather_el_cajon>{{cite web|url=http://www.weather.com/outlook/travel/businesstraveler/wxclimatology/monthly/92020|title=Monthly Averages for El Cajon, CA|access-date=April 22, 2009|publisher=[[The Weather Channel (United States)|The Weather Channel]]|archive-url=https://web.archive.org/web/20110604055354/http://www.weather.com/outlook/travel/businesstraveler/wxclimatology/monthly/92020|archive-date=June 4, 2011}}</ref> Even in the absence of June gloom, inland areas experience much more significant temperature variations than coastal areas, where the ocean serves as a moderating influence. Thus, for example, downtown San Diego averages January lows of {{convert|50|F|C}} and August highs of {{convert|78|F|C}}. The city of [[El Cajon, California|El Cajon]], just {{convert|12|mi|km}} inland from downtown San Diego, averages January lows of {{convert|42|F|C}} and August highs of {{convert|88|F|C}}.

The average surface temperature of the water at Scripps Pier in the [[California Current]] has increased by almost {{convert|3|F-change}} since 1950, according to scientists at [[Scripps Institution of Oceanography]].<ref>{{cite news|author=Lee, Mike|title=Is global warming changing California Current?|url=http://www.signonsandiego.com/news/2011/jun/18/taking-stock-california-current/|date=June 18, 2011|work=U-T (San Diego Union Tribune)|access-date=June 20, 2011}}</ref> Additionally, the mean minimum is now above {{convert|40|F|C}}, putting San Diego in [[hardiness zone]] 11, with the last freeze having occurred many decades ago.

[[File:SurfPacificBeach.jpg|thumb|Surfers at [[Pacific Beach, San Diego|Pacific Beach]]]]

Annual rainfall along the coast averages {{convert|10.65|in|mm}} and the median is {{convert|9.6|in|mm}}.<ref>{{cite news |title=''San Diego's average rainfall set to lower level'' |url=http://www.signonsandiego.com/news/2011/mar/16/san-diegos-average-rainfall-set-lower-level/ |newspaper=San Diego Union-Tribune |date=March 16, 2011 |access-date=April 12, 2011}}</ref> The months of December through March supply most of the rain, with February the only month averaging {{convert|2|in|mm}} or more. The months of May through September tend to be almost completely dry. Although there are few wet days per month during the rainy period, rainfall can be heavy when it does fall. Rainfall is usually greater in the higher elevations of San Diego; some of the higher areas can receive {{convert|11|-|15|in|mm}} per year. Variability from year to year can be dramatic: in the wettest years of 1883/1884 and 1940/1941, more than {{convert|24|in|mm|-1}} fell, whilst in the driest years there was as little as {{convert|3.2|in|mm|-1}}. The wettest month on record is December 1921 with {{convert|9.21|in|mm|0}}.

Snow in the city is rare, having been observed only six times in the century-and-a-half that records have been kept. In 1949 and 1967, snow remained on the ground for a few hours in higher locations like [[Point Loma, San Diego|Point Loma]] and [[La Jolla]]. The other three occasions, in 1882, 1946, and 1987, involved flurries but no accumulation.<ref>{{cite web |last=Rowe |first=Peter |url=http://legacy.signonsandiego.com/news/metro/20071213-9999-1n13snowday.html |title=The day it snowed in San Diego |work=San Diego Union Tribune |date=December 13, 2007 |access-date=May 4, 2011 |archive-url=https://web.archive.org/web/20110810074613/http://legacy.signonsandiego.com/news/metro/20071213-9999-1n13snowday.html |archive-date=August 10, 2011 }}</ref> On February 21, 2019, snow fell and accumulated in residential areas of the city, but none fell in the downtown area.<ref>{{cite web |title=Storm brings major snowfall to East County communities |url=https://fox5sandiego.com/weather/south-moving-storm-douses-county-with-rain-snow/ |website=Fox 5 |date=February 21, 2019 |publisher=Fox 5 Digital Team |access-date=February 27, 2021}}</ref>

{{San Diego weatherbox}}
{{notelist}}