Humidity is the concentration of water vapor present in the air. Humid air is moist. Humidity is the most variable characteristic of the atmosphere and is a major factor in weather and climate. Water vapor is the gaseous state of water and is typically invisible to the human eye. Atmospheric water vapor plays an important role in the weather and climate. It regulates air temperate by absorbing thermal radiation from the Sun and Earth and helps generate precipitation.
In weather reports, humidity is expressed as a percentage of the maximum amount of water vapor the air can hold at the same temperature, also known as relative humidity. Temperature determines the humidity capacity of air. As temperatures decrease, a volume of air can hold less water vapor. When the air has a high moisture content (is humid), sweat cannot evaporate, leaving our bodies feeling sticky and hot. Our bodies must work even harder to cool off, resulting in excessive sweating, increased heart rate, increased respiration, and increase rate and depth of blood circulation. Overall, humidity can make the air temperature feel hotter than it is. In states with very hot summers and high humidity, being outside can feel like a burden. On the other hand, having very low humidity can also cause some discomfort. People can experience dry lips and skin and dry and irritated eyes. Most people are the most comfortable at around 30-50% humidity.
Least Humid States in the U.S.
Because humidity is the concentration of water vapor in the air and water vapor comes from the evaporation of water from Earth’s surface, the states with the most humidity have a large presence of water. Given this, states with large desert landscapes and fewer bodies of water can be expected to have lower humidity. States such as Nevada and Arizona have arid climates and are known for their deserts. The majority of the states with the lowest relative humidity are located in the West.
The states with the lowest relative humidity are: Nevada (38.3%), Arizona (38.5%), New Mexico (45.9%), Utah (51.7%), Colorado (54.1%), Wyoming (57.1%), Montana (60.4%), California (61.0%), Idaho (62.4%), and Oklahoma (64.0%). Additionally, if the least humid major cities in the United States are Las Vegas, NV (30.3%); Phoenix, AZ (36.6%), Denver, CO (52.0%), Salt Lake City, UT (55.3%), New York, NY (63.0%), Washington, DC (64.3%); Oklahoma City, OK (64.9%), Dallas, TX (65.4%); Baltimore, MD (65.8%); and Hartfird, CT (66.0%).