PERMFILE44821 - Laserfiche WebLink

Home Browse Search

CLIMATE OF COLORADO Page 2 of 3 frequently too shallow to cross the mountains to the westem portion of the State so while the plains are in the grip of a very severe storm, the weather in the mountains and westem valleys may be mild. Occasionally, when the plains are covered with a shallow layer of cold air, strong westerly winds aloft work their way to the surface. Warmed by rapid descent from higher levels, these winds bring large and sudden temperature rises. This phenomenon is the "chinook" of the high plains and temperature rises of 25 degrees to 35° within a short time are not ^ncommon. Chinook winds greatly moderate average winter temperatures in azeas near enough to [he mountains to experience them frequently. Warm, moist air from the south moves into Colorado most frequently in the spring. As this air is carried nor[hwazd and westward [o higher elevations, the heaviest and most general rainfalls of the yeaz occur over the eastem portions of the State. Frequent showers and thunderstorms continue well into the summer. At times during the summer, winds shift into the southwest and bring hot, dry air over the State_from_ the hottest weather of the year over the eastem plains, but such hot_. spells are usually of short duration. CLIMATE OF THE EASTERN PLAINS -The climate of the plains is compazatively uniform from place to place, with characteristic features of low relatve humidity, abundant sunshine, light rainfall, moderate to high wind movement, and a large daily range in temperature. Summer daily maximum temperatures are often 95° F or above, and 100° F temperatures have been observed at all plain stations. Such temperatures are not infrequent at altitudes below 5,000 feet; above that elevation they are compazatively rare. The highest temperatures in Colorado occur in the northeastern plains, and sometimes exceed 115° F. Because of the very low relative humidity accompanying these high temperatures, hot days cause less discomfort than in more humid azeas. The usual winter extremes in the plains are from zero to 10° F or 15° F below zero. P.rt important feature of the precipitation in the plains is the large proportion of the annual total that falls during [he growing season - 70 to 80 percent during the period from April through September. Summer precipitation in the plains is largely from thunderstorm activity and is sometimes extremely heavy. Strong winds occur frequently in winter and C spring. These winds tend to dry out soils, which aze not well supplied with moisture because of the low annual precipitation. During periods of drought, high winds give rise to the dust storms which are especially characteristic of the southeastern plains. At the western edge of the plains and neaz the foothills of the mountains, there are a number of significant changes in climate as compared to the plains proper. Average wind movement is less, but areas very near the mountains are subject [o periodic, severe turbulent winds from the effects of high westerly winds over the mountain barrier. Temperature changes from day to day are not as great; summer temperaures are lower, and winter temperatures are higher. Precipitation, which decreases gradually from the eastem border to a minimum near the mountains, increases rapidly with the increasing elevation of the foothills and increases rapidly with the increasing elevation of the foothills and proximity to higher ranges. The decrease in temperature from the eastern boundary westward to the foothills is less than might be expected with increasing altitude. This results from mountain and valley winds and greater frequency of the chinook. Below the Royal Gorge of the Arkansas, the mountain and valley winds aze strong enough to modify the climate over a considerable area. Descending air currents frequently prevent the stratification of air necessary for the occurrence of excessive cold. As a consequence, the winter climate is milder than elsewhere in [he Slate. CLIMATE OF WESTERN COLORADO -The rugged topography of westem Colorado causes lazge variations in climate within short distances, and few climatic generalizations apply to the whole area. A[ [he summits of mountains, temperatures are low, averaging less than 32° F over [he year. Snow-covered mountain peaks and valleys often have very cold nighttime temperatures in winter, when skies are clear and the air is still -occasionally to 50° F below zero. Summer in the mountains is a cool and refreshing season. At typical mountain stations the average July temperature is in the neighborhood of 60° F. The highest temperatures are usually in the seventies and eighties, but may reach 90° F to 95° F. Above 7,000 feet, the nights are quite cool throughout the summer, while bright sunshine makes the days comfortably warm. The lower western valleys of the State are protected by surrounding high terrain, and have a greater uniformity of weather than the eastern plains. They experience high summer temperatures, comparable to those of the eastern plains, while average winter temperatures are somewhat lower than at simiht elevations in the plains, due largely to the relative infrequency of chinook of other warming winds. Precipitation west of the Continental Divide is more evenly distributed throughout the yeaz than in the eastern plains. For most of western Colomdo, the greatest monthly precipitation occurs in the winter months, while June is the driest month.