Editing Geography of the United States (section)

==Climate==
{{Main|Climate of the United States}}
[[File:US_50_states_Köppen_with_territories.png|thumb|The [[Köppen climate classification|Köppen climate types]] of the United States, including the five inhabited [[Territories of the United States|U.S. territories]])]]
[[File:Average precipitation in the lower 48 states of the USA.png|thumb|A map of average precipitation across the contiguous United States]]
Due to its large size and wide range of geographic features, the United States contains examples of nearly every global climate. The climate is subtropical in the [[Southern United States]], [[humid continental climate|continental]] in the north, tropical in [[Hawaii]] and southern [[Florida]], polar in Alaska, semiarid in the Great Plains west of the [[100th meridian west|100th meridian]], Mediterranean in coastal [[California]] and arid in the [[Great Basin]] and the [[Southwestern United States|Southwest]]. Its comparatively favorable agricultural climate contributed (in part) to the country's rise as a world power, with infrequent severe drought in the major agricultural regions, a general lack of widespread flooding, and a mainly temperate climate that receives adequate precipitation.

The main influence on U.S. weather is the [[jet stream|polar jet stream]] which migrates northward into Canada in the summer months, and then southward into the US in the winter months. The jet stream brings in large low-pressure systems from the northern [[Pacific Ocean]] that enters the US mainland over the Pacific Northwest. The [[Cascade Range]], [[Sierra Nevada (U.S.)|Sierra Nevada]], and [[Rocky Mountains]] pick up most of the moisture from these systems as they move eastward via the [[Precipitation (meteorology)#Orographic effects|orographic effect]], and they are greatly diminished by the time they reach the High Plains.

Once they move over the Great Plains, uninterrupted flat land allows them to reorganize and can lead to major clashes of air masses. In addition, moisture from the [[Gulf of Mexico]] is often drawn northward. When combined with a powerful jet stream, this can lead to violent thunderstorms, especially during spring and summer. Sometimes during winter, these storms can combine with another low-pressure system as they move up the East Coast and into the [[Atlantic Ocean]], where they intensify rapidly.
These storms are known as [[Nor'easter]]s and often bring widespread, heavy rain, wind, and snowfall to [[New England]]. The uninterrupted grasslands of the Great Plains also lead to some of the most extreme climate swings in the world. Temperatures can rise or drop rapidly, winds can be extreme, and the flow of heat waves or Arctic air masses often advance uninterrupted through the plains.

The [[Great Basin]] and [[Columbia Plateau]] (the [[Intermontane Plateaus]]) are arid or semiarid regions that lie in the rain shadow of the [[Cascade Mountains|Cascades]] and [[Sierra Nevada (U.S.)|Sierra Nevada]]. Precipitation averages less than {{convert|15|in|cm|0}}. The Southwest is a hot desert, with temperatures exceeding {{convert|100|°F|1}} for several weeks at a time in summer. The Southwest and the Great Basin are also affected by the [[monsoon]] from the [[Gulf of California]] from July to September, which brings localized but often severe thunderstorms to the region.

Much of California consists of a [[Mediterranean climate]], with sometimes excessive rainfall from October–April and nearly no rain the rest of the year. In the [[Pacific Northwest]] rain falls year-round but is much heavier during winter and spring. The mountains of the west receive abundant precipitation and very heavy snowfall. The Cascades are one of the snowiest places in the world, with some places averaging over {{convert|600|in|cm|0}} of snow annually, but the lower elevations closer to the coast receive very little snow.

Florida has a [[subtropical climate]] in the northern part of the state and a [[tropical climate]] in the southern part of the state. Summers are wet and winters are dry in Florida. Annually, much of Florida and the deep southern states is frost-free. The mild winters of Florida allow a massive tropical fruit industry to thrive in the central part of the state, making the US second to only Brazil in [[citrus production]] worldwide.

Another significant (but localized) weather effect is [[lake-effect snow]] that falls south and east of the [[Great Lakes]], especially in the hilly portions of the [[Upper Peninsula]] of [[Michigan]] and on the [[Tug Hill Plateau]] in [[New York (state)|New York]]. The lake effect dumped well over {{convert|5|ft|m|2}} of snow in the area of Buffalo, New York throughout the 2006–2007 winter. The [[Wasatch Front]] and [[Wasatch Range]] in [[Utah]] can also receive significant lake effect accumulations from the [[Great Salt Lake]].<gallery>
File:Climate map USA.PNG|'''Climate map USA'''
File:Mitchell Map-06full2.jpg|'''Mitchell Map-06full2'''
</gallery>

===Extremes===
{{see also|U.S. state temperature extremes}}
[[File:Fagatogo Dock.jpg|thumb|[[Pago Pago Harbor]] in [[American Samoa]] has the highest annual rainfall of any harbor in the world.<ref name="LonelyplanetAS">{{cite web|url=https://www.lonelyplanet.com/american-samoa/tutuila/attractions/rainmaker-mountain/a/poi-sig/1456093/362248|author=Lonely Planet|title=Rainmaker Mountain in Tutuila|website=Lonely Planet|access-date=September 1, 2019|archive-url=https://web.archive.org/web/20171019004653/https://www.lonelyplanet.com/american-samoa/tutuila/attractions/rainmaker-mountain/a/poi-sig/1456093/362248|archive-date=October 19, 2017|url-status=live}}</ref>]]
In northern [[Alaska]], [[tundra]] and [[arctic]] conditions predominate, and the temperature has fallen as low as {{convert|-80|°F|1}}.<ref>Williams, Jack [https://www.usatoday.com/weather/wcstates.htm Each state's low temperature record], ''USA today'', ''URL accessed 13 June 2006.''</ref> On the other end of the spectrum, [[Death Valley National Park|Death Valley, California]] once reached {{convert|134|°F|1}}, the highest temperature ever recorded on Earth.<ref name="Death_Valley">{{cite web | url = http://www.nps.gov/deva/planyourvisit/upload/Weather.pdf | title = Weather and Climate | access-date = October 5, 2006 |date=January 2002 | work = Official website for Death Valley National Park | publisher = National Park Service U. S. Department of the Interior | pages = 1–2}}</ref><ref>{{cite web|url=http://www.wmo.int/pages/mediacentre/press_releases/pr_956_en.html |title=WMO Press release No. 956 |date=September 13, 2012 |publisher=World Meteorological Organization |access-date=April 10, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160406053728/http://www.wmo.int/pages/mediacentre/press_releases/pr_956_en.html |archive-date=April 6, 2016 }}</ref>

On average, the mountains of the western states receive the highest levels of snowfall on Earth. The greatest annual snowfall level is at [[Mount Rainier]] in [[Washington (state)|Washington]], at {{convert|692|in|cm|0}}; the record there was {{convert|1122|in|cm|0}} in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported {{convert|1140|in|cm|0}} of snowfall for the 1998–99 snowfall season. Other places with significant snowfall outside the Cascade Range are the [[Wasatch Mountains]] in [[Utah]], the [[San Juan Mountains]] in [[Colorado]], and the [[Sierra Nevada (U.S.)|Sierra Nevada]] in [[California]].

In the east, the region near the Great Lakes and the mountains of the Northeast receive the most snowfall, although they do not near snowfall levels in the western United States. Along the northwestern Pacific coast, rainfall is greater than anywhere else in the continental U.S., with [[Quinault Rainforest]] in Washington having an average of {{convert|137|in|cm|0}}.<ref>National Atlas, [http://www.nationalatlas.gov/mld/prism0p.html Average Annual Precipitation, 1961–1990] {{webarchive|url=https://web.archive.org/web/20060928220607/http://nationalatlas.gov/mld/prism0p.html |date=2006-09-28 }}, ''URL accessed 15 June 2006.''</ref> Hawaii receives even more, with {{convert|404|in|cm|0}} measured annually in the [[Big Bog, Maui|Big Bog]], in [[Maui]].<ref>{{cite web| url = https://scholarspace.manoa.hawaii.edu/handle/10125/36675| title = ScholarSpace at University of Hawaii at Manoa: Climatology of Haleakalā| date = July 2015| hdl = 10125/36675| last1 = Longman| first1 = Ryan J.| last2 = Giambelluca| first2 = Thomas W.| last3 = Nullet| first3 = Michael A.| last4 = Loope| first4 = Lloyd L.}} R.J. Longman and T.W. Giambelluca. Climatology of Haleakala. Climatology of Haleakalā Technical Report No. 193. Volume 1, Issue 1. Pages 105–106. 2015. Retrieved September 1, 2019.</ref> [[Pago Pago Harbor]] in [[American Samoa]] is the rainiest harbor in the world (because of the 523 meter [[Rainmaker Mountain]]).<ref name="LonelyplanetAS"/> The [[Mojave Desert]], in the southwest, is home to the driest locale in the U.S. [[Yuma, Arizona]], has an average of {{convert|2.63|in|cm}} of [[precipitation (meteorology)|precipitation]] each year.<ref>Hereford, Richard, et al., [http://pubs.usgs.gov/fs/fs117-03/ Precipitation History of the Mojave Desert Region, 1893–2001], ''U.S. Geological Survey, Fact Sheet 117-03'', ''URL accessed 13 June 2006.''</ref>

In central portions of the U.S., [[tornado]]es are more common than anywhere else on Earth<ref>NOVA, [https://www.pbs.org/wgbh/nova/tornado/country.html Tornado Heaven], ''Hunt for the Supertwister'', ''URL accessed 15 June 2006.''</ref> and touch down most commonly in the spring and summer. Deadly and destructive [[hurricane]]s occur almost every year along the Atlantic seaboard and the Gulf of Mexico. The Appalachian region and the Midwest experience the worst floods, though virtually no area in the U.S. is immune to flooding. The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have hurt [[Ancestral Pueblo peoples]].<ref>O'Connor, Jim E. and John E. Costa, [http://pubs.usgs.gov/circ/2003/circ1245/ Large Floods in the United States: Where Thley Happen and Why], ''U.S. Geological Survey Circular 1245'', ''URL accessed 13 June 2006.''</ref> The West is affected by large wildfires each year.