The United States of America is the third or fourth largest country in the world (depending on how its total area is calculated), with an area of approximately 9,833,520 km2. Given its large size, the amount and frequency of precipitation vary significantly across the country. For example, during the late summer and fall, extratropical storms bring significant rainfall to certain different parts of the US, and in the fall, winter, and spring, the western US and the archipelagic state of Hawaii receive substantial rainfall from Pacific storm systems. Additionally, rainfall is relatively evenly distributed throughout the year in the upper eastern and central parts of the country. Therefore, various patterns of rainfall distribution and intensity are evident in the 50 US states. While Hawaii, Louisiana, Mississippi, Alabama, and Florida are the wettest US states, Nevada, Arizona, Utah, New Mexico, and Wyoming are the driest.
The 5 Driest US States
Nevada is the driest state in the US. The state is located in the western part of the country and experiences an arid or semi-arid climate. With the exception of the Las Vegas Valley, most of Nevada has an average diurnal temperature of 22 °C during the summer. In the northern part of the state, winters are cold and long, while the season is short and mild in southern Nevada. Rainfall is low throughout the state, although the leeward side of the Sierra Nevada Mountains, which run through Nevada, receives more rainfall. The state has an average annual rainfall of only 10.3 inches and an average monthly rainfall of just 0.7 inches. Most rain in Nevada occurs in January.
Arizona is America’s second driest state. Located in the southwestern part of the country, Arizona's climate is not uniform but varies considerably within the state due to its vast size and varying elevation. Areas at lower altitudes experience a desert climate, with extremely hot summers and mild winters. The hottest months are June to September, while winter lasts from November until February. Arizona receives only 12.6 inches of average annual rainfall and 0.9 inches of average monthly rainfall. August is the rainiest month in the state, although rain occurs during both the summer and winter seasons. During summer, monsoons are responsible for rain, while in winter the cold fronts arising from the Pacific Ocean bring rain. When rain falls in Arizona, it is often in the form of sudden downpours accompanied by thunderstorms, lightning, and wind. Flash floods are also common during these storms. A cooler climate prevails in the plateau region of Arizona.
Utah, the third driest US state, is located in the western part of the country. The climate of Utah varies from semi-arid to desert, and summers are very hot, while winters are very cold. Due to the presence of numerous mountains in the state, Utah's climate also varies according to altitude. Utah has an average annual and monthly rainfall of 13.6 inches and 1.1 inches, respectively, and April is the rainiest month of the year. The state's location in the rain shadow region of the Sierra Nevada is primarily responsible for its low precipitation. Therefore, all rainfall received is due to the influence of the Pacific Ocean, which also makes Utah prone to storms. Additionally, monsoon winds can bring rainfall. With less than 5 inches of average annual rainfall, the Great Salt Lake Desert is the driest part of Utah.
4. New Mexico
New Mexico is the fourth driest state in the US. Located in the southwestern part of the country, New Mexico’s climate ranges from semiarid to arid. However, some parts of the state experience alpine and continental climates. The state’s landscape is dominated by vast stretches of desert, high plains, and mountains. New Mexico receives average annual and monthly rainfall of only 14 inches and 1.1 inches, respectively. August is the rainiest month in the state.
Located in the mountain region of the United States, Wyoming is the fifth driest state in the country. It is also the least populous US state. Wyoming’s climate ranges from semi-arid to continental, and it experiences greater temperature extremes than most parts of the country. Summers are relatively warm, but the temperature drops steadily with elevation. Winters are extremely cold in most parts of Wyoming. The state experiences an average annual rainfall of 15.9 inches and an average monthly rainfall of 1.2 inches. Most precipitation occurs in late spring to early summer, and May is the rainiest month. However, rainfall is not uniform throughout the state. In lower areas of the Big Horn Basin, only 5 to 8 inches of average annual rainfall is recorded, making the area a true desert. In the eastern plains and the northern lower areas, about 10 to 12 inches of rainfall is recorded annually, which makes these parts semi-arid. Greater amounts of rain, and even snow, occur in certain mountain areas of Wyoming.
Many of the driest US states are located in the southwestern part of the country. Some climatologists predict that this area will become even drier and warmer in the future due to climate change. Such changes in temperature and precipitation will adversely impact agriculture, and will also lead to longer and more frequent droughts, which will further strain available water resources in this region of the United States.