Arizona (/ɛərɪˈzoʊnə, ærɪ-/ ( listen); Navajo: Hoozdo Hahoodzo [xòːztò xɑ̀xòːtsò]; O'odham: Alĭ ṣonak [ˡaɺi ˡʂonak]) is a state in the southwestern region of the United States. It is also part of the Western and the Mountain states. It is the sixth largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is one of the Four Corners states. It has borders with New Mexico, Utah, Nevada, California, and Mexico, and one point in common with the southwestern corner of Colorado. Arizona's border with Mexico is 389 miles (626 km) long, on the northern border of the Mexican states of Sonora and Baja California.
Arizona is the 48th state and last of the contiguous states to be admitted to the Union, achieving statehood on February 14, 1912. Historically part of the territory of Alta California in New Spain, it became part of independent Mexico in 1821. After being defeated in the Mexican–American War, Mexico ceded much of this territory to the United States in 1848. The southernmost portion of the state was acquired in 1853 through the Gadsden Purchase.
Southern Arizona is known for its desert climate, with very hot summers and mild winters. Northern Arizona features forests of pine, Douglas fir, and spruce trees; the Colorado Plateau; some mountain ranges (such as the San Francisco Mountains); as well as large, deep canyons, with much more moderate summer temperatures and significant winter snowfalls. There are ski resorts in the areas of Flagstaff, Alpine, and Tucson. In addition to the Grand Canyon National Park, there are several national forests, national parks, and national monuments.
About one-quarter of the state is made up of Indian reservations that serve as the home of 27 federally recognized Native American tribes, including the Navajo Nation, the largest in the state and the United States, with more than 300,000 citizens. Although federal law gave all Native Americans the right to vote in 1924, Arizona excluded those living on reservations from voting until its state Supreme Court ruled in 1948 in favor of Native American plaintiffs.
Due to its large area and variations in elevation, the state has a wide variety of localized climate conditions. In the lower elevations, the climate is primarily desert, with mild winters and extremely hot summers. Typically, from late fall to early spring, the weather is mild, averaging a minimum of 60 °F (16 °C). November through February are the coldest months, with temperatures typically ranging from 40 to 75 °F (4 to 24 °C), with occasional frosts.
About midway through February, the temperatures start to rise, with warm days, and cool, breezy nights. The summer months of June through September bring a dry heat from 90–120 °F (32–49 °C), with occasional high temperatures exceeding 125 °F (52 °C) having been observed in the desert area. Arizona's all-time record high is 128 °F (53 °C) recorded at Lake Havasu City on June 29, 1994, and July 5, 2007; the all-time record low of −40 °F (−40 °C) was recorded at Hawley Lake on January 7, 1971.
Due to the primarily dry climate, large diurnal temperature variations occur in less-developed areas of the desert above 2,500 feet. The swings can be as large as 83 °F (28 °C) in the summer months. In the state's urban centers, the effects of local warming result in much higher measured night-time lows than in the recent past.
Arizona has an average annual rainfall of 12.7 in (323 mm), which comes during two rainy seasons, with cold fronts coming from the Pacific Ocean during the winter and a monsoon in the summer. The monsoon season occurs toward the end of summer. In July or August, the dewpoint rises dramatically for a brief period. During this time, the air contains large amounts of water vapor. Dewpoints as high as 81 °F (27 °C) have been recorded during the Phoenix monsoon season. This hot moisture brings lightning, thunderstorms, wind, and torrential, if usually brief, downpours. These downpours often cause flash floods, which can turn deadly. In an attempt to deter drivers from crossing flooding streams, the Arizona Legislature enacted the Stupid Motorist Law. It is rare for tornadoes or hurricanes to occur in Arizona.
Arizona's northern third is a plateau at significantly higher altitudes than the lower desert, and has an appreciably cooler climate, with cold winters and mild summers, though the climate remains semiarid to arid. Extremely cold temperatures are not unknown; cold air systems from the northern states and Canada occasionally push into the state, bringing temperatures below 0 °F (−18 °C) to the state's northern parts.
Indicative of the variation in climate, Arizona is the state which has both the metropolitan area with the most days over 100 °F (38 °C) (Phoenix), and the metropolitan area in the lower 48 states with the most days with a low temperature below freezing (Flagstaff).
Average daily maximum and minimum temperatures for selected cities in Arizona
LocationJuly (°F)July (°C)December (°F)December (°C)