Denver, Colorado, often referred to as the Mile High City, has a climate that surprises many visitors. The city is famous for its abundant sunshine, averaging over 300 days of sun each year. This reputation is accurate, as Denver sits in a semi-arid steppe climate zone, making it much drier than many other major American cities. To understand Denver’s precipitation, it is necessary to consider the total moisture received throughout the year, not just rainfall.
Total Annual Precipitation
The average amount of moisture Denver receives annually, known as total precipitation, typically falls in the range of 14 to 17 inches. This figure represents the liquid water equivalent from all sources, including rain, melted snow, hail, and sleet. Compared to the United States national average of 38 inches, Denver is a relatively dry metropolitan area. The low total precipitation is a defining characteristic of the city’s climate. This scarcity places Denver firmly within the high-plains semi-arid classification.
The Importance of Snowfall
A significant portion of Denver’s annual precipitation comes in the form of snow, rather than rain. On average, the city receives between 50 and 60 inches of snow each year. This high snowfall total is deceiving when considering the liquid precipitation amount. Snow is far less dense than rain, which is accounted for using the snow-to-liquid ratio. A typical ratio is 10:1, meaning ten inches of fresh snow melts down to just one inch of liquid water.
Therefore, the 50 to 60 inches of annual snowfall only contributes about five to six inches to the overall liquid precipitation total. This conversion explains why a large snowfall amount does not translate into a high annual precipitation figure.
Monthly and Seasonal Trends
Denver’s precipitation is not distributed evenly throughout the year, featuring distinct wet and dry seasons. The heaviest precipitation tends to occur during the spring and early summer months. May is consistently the wettest month, often recording over two inches of moisture. This period is characterized by the convergence of Pacific storm systems and moist air from the Gulf of Mexico, leading to increased rainfall and occasional thunderstorms.
Conversely, the winter months, typically December through February, are the driest in terms of total liquid precipitation. Although snow falls during this period, the frequency and total liquid accumulation are lower, making winter the season with the least moisture input.
Geographic Factors Shaping Denver’s Climate
The primary reason for Denver’s low annual precipitation totals is its unique geographic position relative to the Rocky Mountains. The city is situated on the High Plains, immediately east of the Front Range. This mountain barrier creates a phenomenon known as the rain shadow effect.
When moisture-laden air masses move from the west, they are forced upward by the mountains, a process called orographic lifting. As the air rises, the moisture condenses and precipitates mostly on the western, or windward, side of the range. By the time the air descends on the eastern, or leeward, side where Denver is located, it is significantly drier. This process effectively wrings the moisture out of the atmosphere before it reaches the city.