General Climate
Colorado is far enough away from major sources of moisture to experience much in the way of rain. The elevation of the state and its location in North America creates a dry, cool atmosphere throughout the year, with warm days and cold nights.
Average Rainfall
Between 1961 and 1990, the average rainfall in the driest areas of Colorado was only between 5.1 and 10 inches per year. These areas include the southern plains surrounding the Rio Grande. The areas that see the most rainfall fall on the western end of the state, where generally between 35 and 60 inches of rain fall per year, depending on elevation. Overall, the state sees an average of 15.47 inches of rain per year.
Storms
Storms in Colorado do not necessarily bring more rain but when they do, it can be a lot in a short amount of time. Those that come in from the north drop temperatures and bring enough moisture to sometimes create blizzards in the mountains. Localized, intense thunderstorms, often in the eastern plains region, are known to dump large amounts of rain that can result in flash flooding.