page_title: Geography of Arizona
section_title: Rainfall
hierarchical_section_title: Geography of Arizona / Climate / Rainfall
caption_attribution_description: English: Map of the average precipitation in Arizona.
context_page_description: Arizona is a landlocked state situated in the southwestern region of the United States of America. It has a vast and diverse geography famous for its deep canyons, high- and low-elevation deserts, numerous natural rock formations, and volcanic mountain ranges. Arizona shares land borders with Utah to the north, the Mexican state of Sonora to the south, New Mexico to the east, and Nevada to the northwest, as well as water borders with California and the Mexican state of Baja California to the southwest along the Colorado River. Arizona is also one of the Four Corners states and is diagonally adjacent to Colorado.
  Arizona has a total area of 113,998 square miles, making it the sixth largest U.S. state. Of this area, just 0.32% consists of water, which makes Arizona the state with the second lowest percentage of water area. Arizona spans about 335 miles at its widest and 390 miles at its longest, and has an average elevation of about 4,000 feet. The geographic center of Arizona is located in Yavapai County, approximately 55 miles east-southeast of the city of Prescott.
context_section_description: Precipitation in Arizona is governed by elevation and the season of year. The peak periods of rainfall are during the early winter, when storm systems from the Pacific Ocean cross the state, and during the summer, then moisture-bearing winds sweep into Arizona from the southeast, which obtain moisture from the Gulf of Mexico. Summer rains tend to occur in the form of thunderstorms, which result from excessive heating of the ground and the lifting of moisture-laden air along mountain ranges. These thunderstorms can cause strong winds, brief periods of blowing dust, and infrequently cause hail. The heaviest precipitation is found in the mountain ranges of central and southeastern Arizona, while the driest conditions are found in the arid regions of southwestern Arizona.
  The number of days with measurable precipitation can vary from around 70 in the Flagstaff area to 15 in the Yuma area. The highest elevations of Arizona receive up to 30 inches (760 mm) of precipitation annually, and the southern slopes of the Mogollon Rim and the southeast average between 15 and 20 inches (380 and 510 mm). The driest part of the state is the southwestern region, which receives under 3 inches (76 mm) of rain a year, whilst the northeastern Colorado Plateau is in a rain shadow and receives between 4.5 and 10 inches (114 and 254 mm). Annual average humidity values vary from 55% in Flagstaff to 23% in Yuma. Due to the high temperatures, low humidity, and occurrence of sunshine, Arizona has high rates of evaporation. Average annual lake evaporation varies from about 80 inches (2,000 mm) in the southwestern part of the state to about 50 inches (1,300 mm) in the northeast.
caption: A map of Arizona's average rainfall
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