Climate of Phoenix
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Phoenix has a hot desert climate (Köppen: BWh),[1][2] typical of the Sonoran Desert, and is the largest city in America in this climatic zone.[3] Phoenix has long, extremely hot summers and short, mild winters. The city is within one of the world's sunniest regions, with its sunshine duration comparable to the Sahara region. With 3,872 hours of bright sunshine annually, Phoenix receives the most sunshine of any major city on Earth.[4] Average high temperatures in summer are the hottest of any major city in the United States.[5] On average, there are 111 days annually with a high of at least 100 °F (38 °C), including most days from the end of May through late September. Highs top 110 °F (43 °C) an average of 21 days during the year.[6] On June 26, 1990, the temperature reached an all-time recorded high of 122 °F (50 °C).[7]
In 2024, Phoenix-Mesa, AZ, was ranked fifth for most ozone pollution in the United States according to the American Lung Association.[8] Vehicle emissions are cited as precursors to ozone formation. Phoenix also has high levels of particulate pollution; although, cities in California lead the nation in this hazard.[9] PM2.5 particulate matter, which is a component of diesel engine exhaust, and larger PM10 particles, which can come from dust, can both reach concerning levels in Phoenix.[10] In fact, people, pets, and other animals exposed to high concentrations of PM10 dust particles―primarily from dust storms or from disturbed agricultural or construction sites―are at risk of contracting Valley Fever, a fungal lung infection.[11]
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 "Rethinking cities in the face of extreme heat", Mayor Kate Gallego of Phoenix and others, Knowable Magazine, 2022 |
Unlike most desert locations which have drastic fluctuations between day and nighttime temperatures, the urban heat island effect limits Phoenix's diurnal temperature variation.[12] As the city has expanded, average summer low temperatures have been steadily rising. Pavement, sidewalks, and buildings store the Sun's heat and radiate it at night.[13] The daily normal low remains at or above 80 °F (27 °C) for an average of 74 days per summer.[6] On July 19, 2023, Phoenix set its record for the warmest daily low temperature, at 97 °F (36 °C).[6]
The city averages approximately 300 days of sunshine, or over 85% of daylight hours, per year,[14][15] and receives scant rainfall―the average annual total at Phoenix Sky Harbor International Airport is 7.22 in (183 mm). The region's trademark dry and sunny weather is interrupted by sporadic Pacific storms in the winter and the arrival of the North American monsoon in the summer.[16] Historically, the monsoon officially started when the average dew point was 55 °F (13 °C) for three days in a row—typically occurring in early July. To increase monsoon awareness and promote safety, however, the National Weather Service decreed that starting in 2008, June 15 would be the official "first day" of the monsoon, and it would end on September 30.[citation needed] When active, the monsoon raises humidity levels and can cause heavy localized precipitation, flash floods, hail, destructive winds, and dust storms[17]—which can rise to the level of a haboob in some years.[18]
August is the wettest month (0.93 in (24 mm)), while June is the driest (0.02 in (0.51 mm)). On September 8, 2014, the city of Phoenix recorded its single highest rainfall total by the National Weather Service with 3.30 in (84 mm), breaking the 75-year-old record of 2.91 in (74 mm), set on September 4, 1939.[19] The September 2014 storm was created from the remnants of Hurricane Norbert which had moved up from the Gulf of California and flooded the city's major interstates and low-lying roadways, stranding hundreds of motorists.[16][20] On average, dew points range from 31 °F (−1 °C) in April to 58 °F (14 °C) in August.[21] Occasionally, dew points can drop as low as 0 °F (−18 °C), or they can exceed 70 °F (21 °C) during periods of strong monsoon activity—creating muggy conditions in the area.[22][16][23]
Desert lands in and around the city have become increasingly susceptible to wildfire outbreaks. Fire risk is highest in the dry spring and summer months following wet winters, due to the resulting carpet of invasive buffelgrass, weeds, and brush. Rugged terrain often makes firefighting efforts difficult. Because many desert plants are not adapted to fire, wildfires pose a considerable threat to the future of the local desert ecosystem.[24][25][26]
Generally speaking, the annual minimum temperature in Phoenix is in the mid-to-low 30s. It rarely drops to 32 °F (0 °C) or below, having done so in only nine of the years between 1991 and 2020 on a total of seventeen days.[6] However, peripheral portions of the Phoenix metropolitan area frequently see frost in the winter. The earliest freeze on record occurred on November 4, 1956, and the latest occurred on March 31, 1987.[a] The all-time lowest recorded temperature in Phoenix was 16 °F (−9 °C) on January 7, 1913, while the coldest daily high temperature ever recorded was 36 °F (2 °C) on December 10, 1898. The longest continuous stretch without a day of frost in Phoenix was nearly eight years, from December 27, 1990, to December 23, 1998.[6]
Snow is rare in Phoenix. Snowfall was first officially recorded in 1898, and since then, accumulations of 0.1 inches (0.25 cm) or greater have occurred only eight times within city limits. The heaviest snowstorm on record took place on January 21–22, 1937, when 1 to 4 inches (2.5 to 10.2 cm) fell in parts of the city and did not melt entirely for three days. On December 6, 1998, snow fell across the northwest portions of the city, and Sky Harbor reported a dusting of snow.[27] On February 21–22, 2019, the far northern and northeastern sections of the metro area received several inches of snow while Sky Harbor reported record rainfall.[28] A similar storm impacted the region on March 1, 2023.[29] Between 2010 and 2021, Phoenix experienced three significant winter storms with accumulating, snow-like graupel.[30][31]
| Climate data for Phoenix Int'l, Arizona (1991–2020 normals,[b] extremes 1895–present)[c] | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 88 (31) |
92 (33) |
100 (38) |
105 (41) |
114 (46) |
122 (50) |
121 (49) |
118 (48) |
118 (48) |
113 (45) |
99 (37) |
87 (31) |
122 (50) |
| Mean maximum °F (°C) | 78.2 (25.7) |
82.1 (27.8) |
90.4 (32.4) |
99.0 (37.2) |
105.7 (40.9) |
112.7 (44.8) |
114.6 (45.9) |
113.2 (45.1) |
108.9 (42.7) |
100.7 (38.2) |
88.9 (31.6) |
77.7 (25.4) |
115.7 (46.5) |
| Mean daily maximum °F (°C) | 67.6 (19.8) |
70.8 (21.6) |
78.1 (25.6) |
85.5 (29.7) |
94.5 (34.7) |
104.2 (40.1) |
106.5 (41.4) |
105.1 (40.6) |
100.4 (38.0) |
89.2 (31.8) |
76.5 (24.7) |
66.2 (19.0) |
87.1 (30.6) |
| Daily mean °F (°C) | 56.8 (13.8) |
59.9 (15.5) |
66.3 (19.1) |
73.2 (22.9) |
82.0 (27.8) |
91.4 (33.0) |
95.5 (35.3) |
94.4 (34.7) |
89.2 (31.8) |
77.4 (25.2) |
65.1 (18.4) |
55.8 (13.2) |
75.6 (24.2) |
| Mean daily minimum °F (°C) | 46.0 (7.8) |
49.0 (9.4) |
54.5 (12.5) |
60.8 (16.0) |
69.5 (20.8) |
78.6 (25.9) |
84.5 (29.2) |
83.6 (28.7) |
78.1 (25.6) |
65.6 (18.7) |
53.7 (12.1) |
45.3 (7.4) |
64.1 (17.8) |
| Mean minimum °F (°C) | 36.0 (2.2) |
40.0 (4.4) |
44.4 (6.9) |
50.1 (10.1) |
58.4 (14.7) |
69.4 (20.8) |
74.4 (23.6) |
74.2 (23.4) |
68.3 (20.2) |
53.8 (12.1) |
42.0 (5.6) |
35.4 (1.9) |
33.8 (1.0) |
| Record low °F (°C) | 16 (−9) |
24 (−4) |
25 (−4) |
35 (2) |
39 (4) |
49 (9) |
63 (17) |
58 (14) |
47 (8) |
34 (1) |
27 (−3) |
22 (−6) |
16 (−9) |
| Average precipitation inches (mm) | 0.87 (22) |
0.87 (22) |
0.83 (21) |
0.22 (5.6) |
0.13 (3.3) |
0.02 (0.51) |
0.91 (23) |
0.93 (24) |
0.57 (14) |
0.56 (14) |
0.57 (14) |
0.74 (19) |
7.22 (183) |
| Average precipitation days (≥ 0.01 in) | 3.8 | 4.1 | 3.1 | 1.5 | 1.0 | 0.5 | 3.9 | 4.6 | 2.5 | 2.2 | 2.2 | 4.0 | 33.4 |
| Average relative humidity (%) | 50.9 | 44.4 | 39.3 | 27.8 | 21.9 | 19.4 | 31.6 | 36.2 | 35.6 | 36.9 | 43.8 | 51.8 | 36.6 |
| Average dew point °F (°C) | 32.4 (0.2) |
32.2 (0.1) |
32.9 (0.5) |
31.6 (−0.2) |
34.3 (1.3) |
39.0 (3.9) |
56.1 (13.4) |
58.3 (14.6) |
52.3 (11.3) |
43.0 (6.1) |
35.8 (2.1) |
33.1 (0.6) |
40.1 (4.5) |
| Mean monthly sunshine hours | 256.0 | 257.2 | 318.4 | 353.6 | 401.0 | 407.8 | 378.5 | 360.8 | 328.6 | 308.9 | 256.0 | 244.8 | 3,871.6 |
| Percent possible sunshine | 81 | 84 | 86 | 90 | 93 | 95 | 86 | 87 | 89 | 88 | 82 | 79 | 87 |
| Average ultraviolet index | 3.1 | 4.4 | 6.6 | 8.5 | 9.7 | 10.9 | 11.0 | 10.1 | 8.3 | 5.6 | 3.7 | 2.7 | 7.0 |
| Source 1: NOAA (dew points, relative humidity, and sun 1961–1990)[32][33][34], Weather.com[35] | |||||||||||||
| Source 2: UV Index Today (1995 to 2022)[36] | |||||||||||||
| Climate data for Phoenix | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Mean daily daylight hours | 10.0 | 11.0 | 12.0 | 13.0 | 14.0 | 14.0 | 14.0 | 13.0 | 12.0 | 11.0 | 10.0 | 10.0 | 12.0 |
| Average Ultraviolet index | 3 | 4 | 6 | 8 | 10 | 11 | 11 | 10 | 8 | 6 | 4 | 3 | 6.9 |
| Source: Weather Atlas [37] | |||||||||||||
Time series
[edit] | Graphs are unavailable due to technical issues. There is more info on Phabricator and on MediaWiki.org. |
See or edit raw graph data.
References
[edit]- ^ Since Sky Harbor International Airport (PHX) opened, the earliest and latest freezes recorded there are November 3, 1946, and April 4, 1945, respectively. However, as the official Phoenix climatology station was changed to PHX in October 1953, those records are not considered official.
- ^ Mean monthly maxima and minima (i.e. the highest and lowest temperature readings during an entire month or year) calculated based on data at said location from 1991 to 2020.
- ^ Official records for Phoenix kept at downtown August 1895 to September 1953, and at Sky Harbor Int'l since October 1953. For more information see ThreadEx.
- ^ Kottek, M.; Grieser, J.; Beck, C.; Rudolf, B.; Rubel, F. (2006). "World Map of Köppen–Geiger Climate Classification" (PDF). Climate Change & Infectious Diseases Group, Institute for Veterinary Public Health. University of Veterinary Medicine Vienna. Archived (PDF) from the original on 2009-02-05. Retrieved January 30, 2018.
- ^ Peel, M. C.; Finlayson, B. L.; McMahon, T. A. (October 11, 2007). "Updated world map of the Köppen-Geiger climate classification". Hydrology and Earth System Sciences. 11 (5): 1633–1644. Bibcode:2007HESS...11.1633P. doi:10.5194/hess-11-1633-2007.
- ^ {{Cite le=Phoenix: America's Desert Metropolis | Smart Cities Dive|website=www.smartcitiesdive.com|language=en-US|access-date=March 8, 2019}}
- ^ Stanley, Courtney (April 25, 2016). "The 10 Sunniest Cities In The World". Retrieved September 7, 2016.
- ^ Weatherbee, Caleb (July 9, 2012). "America's Hottest Cities". The Farmer's Almanac. Archived from the original on September 17, 2015. Retrieved August 29, 2015.
- ^ a b c d e "NowData – NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved July 21, 2023.
- ^ Dorish, Joe. "10 All-Time Hottest Weather Temperature Days in Phoenix". Knoji. Retrieved February 5, 2014.
- ^ "Phoenix-Mesa, AZ". www.lung.org. Retrieved 2024-06-22.
- ^ "California Air Quality Report Card". www.lung.org. Retrieved 2021-12-29.
- ^ "New Report: Phoenix Air Quality Worsened for Pollution". American Lung Association. Retrieved September 10, 2019.
- ^ "Valley Fever". Mayo Clinic. Retrieved September 13, 2020.
- ^ Matthew, Rozsa (February 1, 2021). "Why Phoenix may be uninhabitable by the end of this century". Salon. Retrieved February 1, 2021.
- ^ Sirois, Kevin, ed. (2012). Insider's Guide: Phoenix & Scottsdale (7th ed.). Morris Book Publishing. p. 186. ISBN 978-0-7627-7321-3.
- ^ Bulk, Harold. "Abstract on the Climate of Phoenix". Arizona State University. Archived from the original on January 19, 2016. Retrieved March 20, 2016.
- ^ "Weather in the desert covers the spectrum". Arizona Republic. Archived from the original on May 16, 2016. Retrieved March 20, 2016.
- ^ a b c Battaglia, Steven M. (November 1, 2019). "No Fairy Tale Ending: The Future of Water and the American Southwest". Weatherwise. 72 (6): 36–43. doi:10.1080/00431672.2019.1659034. ISSN 0043-1672. S2CID 214466152.
- ^ "Sweeping Dust Storm in Arizona History". Research History. July 8, 2011. Retrieved February 5, 2014.
- ^ Mosbergen, Dominique (June 29, 2015). "Haboob Alert! Giant Dust Storms Engulf Phoenix Area, Leaving Thousands Without Power". HuffPost. Archived from the original on March 31, 2016. Retrieved March 20, 2016.
- ^ "Wettest Day on Record in Phoenix, Flooding Leaves 2 Dead". NBC News. Archived from the original on March 4, 2016. Retrieved September 13, 2014.
- ^ "Record amount of rainfall floods Phoenix as Hurricane Norbert remnants soak Southwest". Fox News Channel. Archived from the original on September 9, 2014. Retrieved September 13, 2014.
- ^ "Average Monthly Dew Point Temperature". westcomp.dp.html. Retrieved October 10, 2021.
- ^ "Arizona State Climate Office: General Geographical and Climatological Summary". asu.edu. Retrieved March 9, 2018.
- ^ "Phoenix Weather Forecasts and Current Conditions: Average Dew Point Summary". TiggrWeather.net. Retrieved June 9, 2020.
- ^ "Arizona wildfire season is already ahead of previous year's pace". KTAR News. June 3, 2020. Retrieved June 3, 2020.
- ^ "Invasive Plant Species: Buffelgrass". NPS.Gov. Retrieved December 6, 2020.
- ^ "What is buffelgrass? Why should I care?". Arizona-Sonora Desert Museum. Retrieved December 6, 2020.
- ^ "A history of snow fall in Phoenix". NOAA. Retrieved December 5, 2011.
- ^ "Snow blankets the desert in north Scottsdale". Azfamily.com. Retrieved April 4, 2021.
- ^ "Major Arizona storm: 'Enormous' amounts of snow, major highways closed, damaging winds, power outages". fox10phoenix.com/news/. February 21, 2023. Retrieved March 3, 2023.
- ^ Haldiman, Philip (December 30, 2010). "Phoenix-area residents report snow falling across Valley". The Arizona Republic. Archived from the original on July 20, 2012. Retrieved February 7, 2011.
- ^ "Sorry to disappoint, Phoenix, but that was graupel, not snow – except in Scottsdale". Azcentral.com. Retrieved April 4, 2021.
- ^ "NowData – NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved 2021-10-10.
- ^ "Summary of Monthly Normals 1991–2020". National Oceanic and Atmospheric Administration. Archived from the original on 2023-07-01. Retrieved 2021-10-11.
- ^ "WMO Climate Normals for PHOENIX/SKY HARBOR INTL, AZ 1961–1990". National Oceanic and Atmospheric Administration. Archived from the original on 2023-07-01. Retrieved 2021-10-10.
- ^ "Monthly Averages for Phoenix, AZ – Temperature and Precipitation". The Weather Channel. Retrieved 2009-05-07.
- ^ "Historical UV Index Data - Phoenix, AZ". UV Index Today. Retrieved April 21, 2023.
- ^ "Phoenix, Arizona, USA – Monthly weather forecast and Climate data". Weather Atlas. Retrieved February 5, 2019.