Editing Thunderstorm (section)

===Severe thunderstorms===
In the United States, a thunderstorm is classed as severe if winds reach at least {{convert|93|km/h|mph}}, hail is {{convert|25|mm|in|0}} in diameter or larger, or if [[funnel cloud]]s or [[tornado]]es are reported.<ref>{{cite web  | title =Weather Glossary – S  | author =National Weather Service  | author-link =National Weather Service | publisher=[[National Oceanic and Atmospheric Administration]] | date =21 April 2005 | url =http://www.weather.gov/glossary/index.php?letter=s  | access-date =17 June 2007 }}</ref><ref>{{cite video  | people = Kim Runk  | title = 1" Hail  | medium = .wmv  | publisher = NOAA  | location = Silver Spring, Maryland|url= http://www.crh.noaa.gov/crh/One_Inch_Hail_Podcast.wmv  |date = 2009}}</ref><ref>{{cite web|url=http://www.wrh.noaa.gov/psr/pns/2009/April/NewHailCriteria.php?wfo=psr|author=[[National Weather Service]] Forecast Office, [[Phoenix, Arizona]]|title=New Hail Criteria|access-date=3 September 2009|date=7 April 2009}}</ref> Although a funnel cloud or tornado indicates a severe thunderstorm, a [[tornado warning]] is issued in place of a [[severe thunderstorm warning]]. A severe thunderstorm warning is issued if a thunderstorm becomes severe, or will soon turn severe. In Canada, a rainfall rate greater than {{convert|50|mm|in|0}} in one hour, or {{convert|75|mm|in|0}} in three hours, is also used to indicate severe thunderstorms.<ref>{{cite web|url=http://www.on.ec.gc.ca/severe-weather/summerwx_factsheet_e.html |title=Fact Sheet – Summer Severe Weather Warnings |author=[[Environment Canada]] Ontario Region |date=24 May 2005 |access-date=3 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090228151724/http://www.on.ec.gc.ca/severe-weather/summerwx_factsheet_e.html |archive-date=28 February 2009 }}</ref> Severe thunderstorms can occur from any type of storm cell. However, [[multicellular thunderstorm|multicell]], [[supercell]], and squall lines represent the most common forms of thunderstorms that produce severe weather.<ref name="motion"/>