Wyoming’s vast, open landscapes often lead to questions about its climate, with many wondering if the state is, in fact, a desert. This perception arises from its arid appearance in many areas, characterized by sparse vegetation and dry conditions. To understand Wyoming’s climate, it is helpful to examine the scientific criteria for defining a desert and apply these to the state’s unique geographical features.
What Defines a Desert?
A desert is a region that receives very low amounts of precipitation, typically less than 10 inches annually. Water loss through evaporation significantly exceeds water gain from precipitation. This imbalance leads to extremely dry conditions where the ground holds little moisture.
Deserts are not solely characterized by high temperatures; they can be hot or cold. Hot deserts, like the Sahara, feature warm, dry summers and can experience extreme daily temperature fluctuations. Cold deserts, such as the Gobi Desert or parts of the Great Basin, have hot or warm, dry summers but are distinguished by cold, dry winters, often with snowfall. These cold deserts are typically found at higher altitudes or in temperate zones. Sparse vegetation that has adapted to arid conditions is another common feature across all desert types.
Wyoming’s Climate and Geography
Wyoming’s climate is largely influenced by its high elevation and the presence of numerous mountain ranges, including the Rockies. The state’s high average elevation contributes to generally cooler temperatures compared to lower-lying regions. This high-altitude, continental climate is typically semi-arid and windier than much of the United States.
Mountain ranges within and surrounding Wyoming create a significant “rain shadow” effect. As moisture-laden air from the Pacific Ocean moves eastward, it is forced upward by the mountains, cooling and releasing much of its precipitation on the western, or windward, slopes. By the time the air descends on the leeward side, it is dry, leading to arid conditions in the basins and plains. This contributes to wide variation in annual precipitation across the state. While some high mountain areas can receive over 60 inches of precipitation annually, largely as snow, lower elevations often receive considerably less. For example, the southwestern portion of Wyoming, a high plateau, receives only 7 to 10 inches of annual precipitation, and the driest part, the Bighorn Basin, can receive as little as 5 to 8 inches.
Understanding Wyoming’s Arid Regions
Wyoming contains significant arid and semi-arid regions that exhibit desert-like characteristics. The Red Desert, located in south-central Wyoming, is one such area, often described as a high-altitude desert and sagebrush steppe. This region includes the Great Divide Basin, a unique area where surface water does not flow out to the ocean. Annual precipitation in these arid regions generally ranges from 4 to 10 inches.
These dry areas support vegetation adapted to limited moisture, primarily sagebrush and perennial grasses. Despite the scarcity of water, these ecosystems host diverse wildlife, including the largest migratory herd of pronghorn in the lower 48 states and a rare desert elk herd. While these areas share the low precipitation and sparse vegetation of deserts, they are commonly classified as arid grasslands or shrublands due to their specific plant communities and often colder winter temperatures. Some classifications consider these high-altitude dry areas as “cold deserts,” aligning with the scientific understanding that deserts are defined by aridity rather than solely by heat.