Colorado’s latitude, elevation and topography, plus its location far inland, work together to produce low humidity and more than 300 days of sunshine each year.
Water Year Average Precipitation for Selected Stations in the I-70 Transect 5.0 4.5
Vail Pass Dillon
3.0 2.5 2.0 1.5 1.0 0.5 0.0
Colorado Statewide Precipitation History: 1895 - 2007 23 22 21 20 19 18
Thompson Flood on July 31, 1976, and the Fort Collins flood of July 28, 1997, are examples of this summertime situation. As summer ends, the atmosphere becomes more stable. Dry air masses from the interior West often replace the more humid summer air from the east and south. Fewer and weaker thunderstorms form. Prolonged episodes of clear, dry weather with deep, blue skies become common, especially near the end of September and in early October. It is not always dry in autumn, however. In fact, near the Utah border, this is often the wettest time of year. Remnants of Pacific hurricanes sometimes move northward and combine with autumn midlatitude storm systems to produce significant rains. The largest floods in the history of southwestern Colorado have nearly all occurred during this time of year. The complex variety of seasonal precipitation patterns experienced across the state makes Colorado unique. Unlike California with its single wet season (winter) and its consistent dry season (summer), Colorado can tap moisture from several sources at different times of year. If winter snows are light, spring storms can make up some of the difference. When spring storms fail, the summer thunderstorms can still help out. If summer storms are few, there is still the chance that hurricane remnants may help. Precipitation, on average, increases with elevation as the map of Colorado average precipitation clearly shows. Elevation gradients are most evident in winter when the strong winds lift air masses up and over the Rockies, squeezing out moisture as they go. At other times of year, the effects of elevation are quite different. During summer, the high elevations help trigger thunderstorms. One thing is very obvious about Colorado. Because of its inland location, moisture doesn’t always get here. Low-pressure troughs may cross the Rockies, but they don’t guarantee precipitation. Over a year, a few major storms that deliver the bulk of the rain and snow, especially over eastern and southern Colorado. If those storms materialize, adequate precipitation falls and life is good. If not, drought and its many impacts appear.
17 16 15 14 13 12 11 Actual Precipitation
9 8 1900
Citizen’s Guide to Colorado Climate Change
Published on Nov 20, 2013