Utah’s environment is defined by its arid or semi-arid climate, making it one of the driest states in the country. Meteorologists use relative humidity to measure the air’s moisture content. This figure indicates the amount of water vapor currently in the air compared to the maximum amount the air could hold at that specific temperature. Utah’s relative humidity remains consistently low throughout the year, though it varies significantly by season and location.
Defining Utah’s General Humidity Levels
Utah is situated in the rain shadow of the Sierra Nevada mountains, which limits the moisture carried by Pacific storms and results in a naturally dry atmosphere. This aridity establishes a low baseline for the state’s average relative humidity. For example, the annual average hovers around 55% for areas like Salt Lake City, but this number is heavily skewed by high morning readings.
The afternoon relative humidity is a more accurate reflection of the daytime climate, frequently dropping below 30% across the state. This low figure explains why Utah’s climate is often referred to as “dry heat” in the summer. For most of the year, the air holds only a fraction of the moisture capacity seen in more temperate or coastal regions.
Seasonal Changes in Humidity
Humidity levels in Utah follow an annual cycle that is largely inverse to the temperature. Winter months, particularly December and January, record the highest relative humidity averages, often peaking in the 70% to 79% range during the morning. This winter increase occurs because cold air holds less moisture overall, meaning less water vapor is needed to reach a higher relative percentage.
The humidity plummets during the summer, reaching its lowest point in July. Afternoon relative humidity in northern metropolitan areas can bottom out around 22%, and in desert valleys, it frequently falls into the single digits. This dramatic shift results from summer’s high temperatures, which vastly increase the air’s moisture-holding capacity, driving the relative humidity percentage down.
Geographic Differences in Humidity Across Utah
Utah’s diverse topography creates a notable humidity gradient from north to south. Northern urban centers, such as Salt Lake City, are situated near the Great Salt Lake and at higher elevations, resulting in slightly higher moisture levels. The lake effect contributes to greater snowfall and can raise localized nighttime humidity in the valleys.
In contrast, Southern Utah, including St. George and desert regions near the Mojave Desert, experiences the most extreme dryness. These lower-elevation areas have significantly less annual precipitation and consistently hotter temperatures. This combination leads to perpetually lower humidity levels throughout the year, making the southern portion of the state the driest.
What Utah’s Low Humidity Means for Daily Life
The persistently low moisture content in the air immediately impacts residents and visitors. A common physical effect is the rapid drying of skin, eyes, and mucous membranes, often leading to nosebleeds and respiratory irritation. Many homeowners use whole-house humidification systems to maintain indoor humidity within the recommended 30% to 50% range.
The low humidity also causes rapid evaporation, which is why high summer temperatures feel more tolerable than in humid climates. However, this rapid evaporation requires people to drink significantly more water to stay hydrated. Furthermore, the dry air increases static electricity, commonly noticeable in homes and vehicles, and can cause wood furniture and flooring to crack or shrink over time.