Tucson, Arizona

===Climate===
Tucson has a hot [[desert climate]] ([[Köppen climate classification|Köppen]] ''BWh''), with two major seasons, a hot summer and mild winter. Tucson averages {{convert|10.61|in|mm|1}} of precipitation per year, concentrated during the Pacific storms of winter and the [[North American Monsoon]] of summer. Fall and spring tend to be sunny and dry.<ref>McKnight & Hess, pp. 212 ''ff'', "Climate Zones and Types: Dry Climates (Zone B)".</ref> Despite being at a more southerly latitude than Phoenix, Tucson is slightly cooler and wetter due to a variety of factors, including elevation and [[orographic lift]] in surrounding mountains, though Tucson does occasionally see warmer daytime temperatures in the winter.<ref>{{cite web |url=https://www.azcentral.com/story/news/local/phoenix-weather/2017/12/01/why-tucson-winter-can-be-warmer-than-phoenix/903557001/ |title=Why Tucson can be warmer than Phoenix in winter |publisher=azcentral.com |access-date=June 13, 2020}}</ref>

[[File:Wasson.jpg|thumb|right|Snow on Wasson Peak]]
[[File:Tucsonmonsoon.jpg|thumb|right|Monsoon clouds blanketed the Catalina Mountains in August 2005.]]
[[File:Saguaro Sunset.jpg|thumb|right|Saguaro at sunset in Saguaro National Park Rincon District]]

Summer is characterized by average daily high temperatures between {{convert|98|and|102|°F|°C|0}} and low temperatures between {{convert|71|and|77|°F|°C|0}}. Early summer is characterized by low humidity and clear skies; mid- and late summer are characterized by higher humidity, cloudy skies, and frequent rain. The sun is intense in Tucson during part of the year, and those who spend time outdoors need protection. Recent studies show that the rate of skin cancer in Arizona is at least three times higher than in more northerly regions. Additionally, [[heat stroke]] is a concern for hikers, mountain bikers, and adventurers who explore canyons, open desert lands, and other exposed areas.<ref>{{cite journal | pmid = 11568742 | doi=10.1067/mjd.2001.114742 | volume=45 | issue=4 | title=Trends in the incidence of nonmelanoma skin cancers in southeastern Arizona, 1985-1996 | journal=J Am Acad Dermatol | pages=528–36 | last1 = Harris | first1 = RB | last2 = Griffith | first2 = K | last3 = Moon | first3 = TE| year=2001 }}</ref>

While monsoon season officially begins on June 15, the arrival of the North American Monsoon is unpredictable, as it varies from year to year. On average, Tucson receives its first monsoon storms around July 3. Monsoon activity generally persists through August and often into September.<ref name="moonsoon-2006">[http://www.wrh.noaa.gov/twc/monsoon/monsoon.php NWS Tucson Office Monsoon tracker] {{Webarchive|url=https://web.archive.org/web/20060818053548/http://www.wrh.noaa.gov/twc/monsoon/monsoon.php |date=August 18, 2006 }}. Retrieved March 12, 2010.</ref> During the monsoon, the [[relative humidity|humidity]] is much higher than the rest of the year. It begins with clouds building up from the south in the early afternoon, followed by intense thunderstorms and rainfall, which can cause [[flash floods]]. The evening sky at this time of year is often pierced with dramatic lightning strikes. Large areas of the city do not have [[storm sewer]]s, so monsoon rains flood the main thoroughfares, usually for no longer than a few hours. A few underpasses in Tucson have "feet of water" scales painted on their supports to discourage fording by automobiles during a rainstorm.<ref>Two underpasses leading towards downtown Tucson from the north, at Sixth Avenue and Stone Avenue, have such "feet of water" scales.</ref> Arizona traffic code Title 28–910, the so-called "Stupid Motorist Law", was instituted in 1995 to discourage people from entering flooded roadways. If the road is flooded and a barricade is in place, motorists who drive around the barricade can be charged up to $2000 for costs involved in rescuing them.<ref>[http://www.azleg.state.az.us/FormatDocument.asp?inDoc=/ars/28/00910.htm&Title=28&DocType=ARS/ Arizona State Legislature, ARS 28–910, Liability for emergency responses in flood areas; definitions] {{Webarchive|url=https://web.archive.org/web/20160923094242/http://www.azleg.state.az.us/FormatDocument.asp?inDoc=%2Fars%2F28%2F00910.htm&Title=28&DocType=ARS%2F |date=September 23, 2016 }}. Retrieved March 12, 2010.</ref> Despite the warnings and precautions, three Tucson drivers have drowned between 2004 and 2010.{{Citation needed|date=May 2017}}

The weather in the fall is much like spring, dry, with warm/cool nights and warm/hot days. Temperatures above {{convert|100|°F|0}} are possible into early October. Temperatures decline at the quickest rate in October and November, and are normally the coolest in late December and early January.

Winters in Tucson are mild relative to other parts of the United States. Average daytime highs range between {{convert|65|and|70|°F|°C|0}}, with overnight lows between {{convert|40|and|44|°F|°C|0}}. Tucson typically averages three hard freezes per winter season, with temperatures dipping to the mid- or low 20s (−7 to −4&nbsp;°C), but this is typically limited to only a very few nights. Although rare, snow occasionally falls in lower elevations in Tucson and is common in the Santa Catalina Mountains. The most recent snowfall was on March 2, 2023, when a [[Early-March 2023 North American storm complex|winter storm]] caused snow to fall throughout most of the southwest. Tucson airport recorded {{convert|1.0|in|cm|abbr=on}} of snow, the seventh heaviest March snowfall on record.<ref>[https://twitter.com/NWSTucson/status/1631321696786579456 The one inch of snow at the Tucson International Airport ranks as the 7th highest March snow. It is also the 10th occurrence of measurable snow in Tucson during March. The highest March snow ampunt was 6.0" (3/12/1922) & overall record 1 day snow is 6.8" (12/8/1971). #azwx], NWS Tucson, ''[[Twitter]]'', March 2, 2023</ref>

Early spring is characterized by gradually rising temperatures and several weeks of vivid wildflower blooms beginning in late February and into March. During this time of year the [[diurnal temperature variation]] normally attains its maximum, often surpassing {{convert|30|F-change}}.

[[File:Monthly Climate Normals (1991-2020) - Tucson Area, AZ(ThreadEx).svg|thumb|right|Climate chart for Tucson]]
Since records began in 1894, the record maximum temperature was {{convert|117|°F|0}} on June 27, 1990, and the record minimum temperature was {{convert|6|°F|0}} on January 7, 1913. There are an average of 158 days annually with highs of {{convert|90|°F|0}} or higher and an average of 12 days with lows reaching or below the freezing mark. Average annual precipitation is {{convert|10.61|in|abbr=on}}. On average, 47.4 days have measurable precipitation. The wettest year was 1905, with {{convert|24.17|in|abbr=on}} and the driest year was 2020 with {{convert|4.16|in|abbr=on}}. The most precipitation in one month was {{convert|8.06|in|abbr=on}} in July 2021. The most precipitation in 24 hours was {{convert|3.93|in|abbr=on}} on July 29, 1958. Annual snowfall averages {{convert|0.1|in|cm|abbr=on}}. The most snow in one winter was {{convert|6.8|in|cm|abbr=on}} in winter 1971–1972. The most snow in one month was {{convert|6.8|in|cm|abbr=on}} in December 1971.

{{Tucson, Arizona weatherbox}}
{{Graph:Weather monthly history
| table=Ncei.noaa.gov/weather/Tucson, Arizona.tab
| title=Tucson monthly weather statistics
}}