Denver is generally a very dry city. The answer to whether it is humid is almost always no, as the city sits in a high-altitude, semi-arid location that naturally limits moisture in the air. This dryness is a direct consequence of its geography, resulting in climate statistics significantly lower than those of coastal or eastern cities. The lack of moisture has noticeable effects on daily life for both residents and visitors. This article explores the data and geographic reasons behind Denver’s low humidity, addresses when those levels can fluctuate, and outlines the practical consequences of living in such a dry environment.
Defining Denver’s Typical Climate
Denver is classified as a cold semi-arid steppe climate, often described as a high desert environment. The city’s elevation, approximately one mile above sea level, is a major factor contributing to low moisture levels. This high altitude means the air is thinner, inherently reducing the total amount of water vapor the atmosphere can hold.
The most significant geographic influence is the city’s position immediately east of the Continental Divide. The Rocky Mountains create the rain shadow effect. As weather systems move from west to east, the mountains force moist air to rise, cool, and release precipitation on the western slope. By the time the air descends on the eastern side, where Denver is located, it has lost much of its moisture. The descending air is also compressed and heated, which further lowers its moisture content, resulting in a naturally dry atmosphere year-round. This geographic barrier fundamentally causes Denver’s low average moisture.
Understanding Denver’s Humidity Data
To quantify Denver’s dryness, it is helpful to look at two specific measurements: Relative Humidity (RH) and Dew Point. Relative humidity is the percentage of moisture currently in the air compared to the maximum amount it can hold at that specific temperature. Denver’s annual average RH is often below 40%, and afternoon readings frequently drop into the 20% range. This is considered very dry compared to coastal cities where averages are often above 60%.
The dew point is a more accurate measure of the actual moisture content, representing the temperature at which the air must be cooled to become fully saturated. Dew point is a better indicator of human comfort; for example, a dew point above 65°F is considered muggy and oppressive. Denver’s typical summer dew point averages in the 40s and low 50s, which is well below the threshold for feeling sticky or humid.
On rare occasions when the dew point climbs into the upper 50s or low 60s, Denver can temporarily feel humid. The low relative humidity, combined with the city’s high-altitude sun, allows for rapid evaporation. This makes the air feel cooler than the temperature reading suggests, which is why a 90-degree day in Denver feels more tolerable than the same temperature in a high-humidity environment.
When Humidity Levels Change
While Denver is consistently dry, seasonal variations cause humidity levels to fluctuate. The most notable change occurs during the North American Monsoon season, typically from mid-July through August. During this period, a shift in wind patterns draws tropical moisture up from the Gulf of Mexico and the Gulf of California.
This seasonal moisture influx can lead to brief, intense afternoon thunderstorms, which temporarily raise the relative humidity and dew point. A cold front moving through the area can also cause a temporary spike in humidity by cooling the air, which increases the relative humidity even if the actual amount of moisture has not changed significantly. However, these spikes are often short-lived, with the air quickly drying out again once the weather system passes.
Conversely, the winter months, especially January and February, often bring the lowest absolute humidity. Cold air naturally holds less water vapor. When the already dry outdoor air is heated inside a home, the indoor relative humidity can plummet, sometimes falling below 20%.
Practical Effects of Low Humidity
The constant lack of moisture in the air has several noticeable effects on the human body. One common issue is the drying of the skin, resulting in flakiness, itching, and chapped lips, as the dry air draws moisture out of the body. The mucous membranes in the nasal passages are also affected, which can lead to irritated sinuses, scratchy throats, and an increased risk of sudden nosebleeds.
Low humidity can also compromise the body’s natural defenses, as the drying of the respiratory tract reduces the clearance of airborne particles and makes the body more susceptible to viruses. Visitors must be mindful of dehydration risk. The combination of high altitude and dry air increases the rate at which moisture evaporates from the body, necessitating a significantly higher water intake than in sea-level environments.
To mitigate these effects, residents and visitors employ strategies to add moisture back into their immediate surroundings. Using a humidifier, especially indoors during the dry winter months, helps maintain a healthier indoor relative humidity between 40% and 60%. Consistent application of moisturizers and lip balm, along with increased consumption of water, are necessary actions for comfort and health in Denver’s arid climate.