Humidity is the concentration of water vapor present in the air. Humidity is a byproduct of the water cycle; as water turns into its gaseous state, water vapor, it begins to fill the air. Atmospheric water vapor also plays an important role in the weather and climate, regulating air temperate by absorbing thermal radiation from the Sun and helping generate precipitation.
Local weathermen typically report relative humidity, a percentage representing the amount of water vapor in the air relative to the maximum amount the air can hold. Temperature determines the humidity capacity of air. As temperatures decrease, air molecules compress and can hold less water vapor. At higher temperatures, the air is capable of holding more water vapor.
Humidity levels affect how temperatures are perceived, as higher levels slow the evaporation of sweat and make it more difficult for bodies to regulate their temperatures, resulting in excessive sweating and increased heart rate and respiration. On the other hand, low humidity can dry skin and allow airborne illnesses to spread more quickly. Most people are the most comfortable at around 30-60% humidity.
As humidity levels rise as water evaporates, the states with the highest levels of humidity have a significant presence of water. On the other hand, states with large desert landscapes and fewer bodies of water typically have lower humidity levels. States such as Nevada and Arizona have arid climates and are known for their deserts.
The states with the lowest relative humidity are:
The least humid major cities in the United States are: