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CLIMATE OF COLORADO Page i of 3 CLIMATE OF COL~RAIDO TOPOGRPHIC FEATURES -Colorado Lies astride the highest mountains of the Continental Divide. Nearly rectangular, its north and south boundaries are the 41° and 37° N. pazallels, and the east and went boundaries are the 102' and I09° W. meridians. It is eighth in size among the 50 states, with an area of 104,247 squaze miles. Although primarily a mountain state, nearly 40 percent of its area is taken up by the eastem high plains. The principal feahres of the Coloradp geography are its inland continental location in the middle latitudes, and the mountains and ranges extending north and south approximately through the middle of the State. With an average altitude of abort 6,800 feet above sea level, Colorado is the highest State in the Union. Roughly three-quarters of the Nation's land above 10,000 feet altitude lies within its borders. The State has 54 mountains 14,000 feet or higher, and about 830 mountains between 11,000 and 14,_000 feet.in elevation. _______ _^ ____ _ Emerging gradually from the plains of Kansas and Nebraska, the high plains of Colorado slope gently upwazd for a distance of some 200 mites from the eastem border to the base of the foothills of the Rocky Mountains. The eastern portion of the State is generally level to rolling prairie broken by occasional hills and bluffs. The northern art of the plains area slopes to the northeast and the southem part to the southeast, divided by higher country and hills extending eastwazd from the mountains near the center of the State. Elevations along the eastem border range from about 3,350 feet at the lowest point in the State (where the Arkansas River crosses the border) to near 4,000 feet. At elevations between 5,000 and b,000 feet the plains give way abruptly to foothills with elevations of 7,000 to 9,000 feet. Backing the foothills are the mountain ranges above 9,000 feet with the higher peaks over 14,000 feet. West of these "front ranges" aze additional ranges, generally extending north and south, but with many spurs and extensions in other directiovs. These ranges enclose numerous high mountain pazks and valleys. Fai[her westward the mountains give way to rugged plateau country in the form of high mesas (some more than 10,000 feet in elevation) which extends to the western border of the State. This land is often cut by rugged canyons, the work of the many steams fed by accumulations of winter snow. \ All rivers in Colorado rise within its borders and flow outward, with the exception of the Green River, which flows \ diagonally across [he extreme northwestern comer of [he State. Four of the Nation's major rivers have their source in Colorado: the Colorado, the Rio Grande, the Arkansas, and the Platte. GENERAL CLIMATE -Most of Colorado has a cool and invigorating climate that could be termed a highland or mountain climate of a continental location. Dying summer there are hot days in the plains, but these aze often relieved by afternoon thundershowers. Mountain regions are neazly always cool. Humidity is generally quite low; this favors rapid evapotranspiration and a relaflvely comfortable feeling even on hot days. The thin atmosphere allows greater penetration of solar radiation and results in pleasant daytime conditions even during the winter. This is why skiers at high elevations are often pictured in very light clothing, although surrounded by heavy snow. The climate of local areas~are profoundly affected by differences in elevation, and to a lesser degree, by [he orientation of mountain ranges and valleys with respect to general air movements. Wide variations occur within short distances. The difference (35°) in annual mean temperature between Pikes Peak and Las Animas, 90 miles to the southeast, is about the same as [hat between southem Florida and Iceland. The average annual snowfall a[ Cubres in the southern mountains is nearly 300 inches; Less than 30 miles away at Manassa in the San Luis Valley, snowfall is Less than 25 inches. While temperature decreases, and precipitation generally increases with altitude, these patterns are modified by the orientation of mountain slopes with respect to the prevailing winds and by the effect of topographical features in creating local air movements. As a result of the State's distance from major sources of moisture Qhe Paeitic Ocean and the Gtilf of Mexico), precipitation is generally light in the lower elevations. Prevailing air currents reach Colorado from westerly directions. Eastward-moving storms originating in the Pacific Ocean lose much of their moishrre falls as rain or snow on [he mountaintops and westward-facing slopes. Eastern slope areas receive relatively small amounts of precipitation from these storms. Storms moving from the north usually carry little moisture. The frequency of such storms increases during the fall and winter months, and decreases rapidly in the spring. The accompanying outbreaks of polar air are responsible for the sadden drops in temperature often experienced in the plains sections of the State. Occasionally these outbreaks are attended by strong northerly winds which come in contact with moist air from the south; the interaction of dtese air masses causes a heavy fall of snow and the most severe of all weather conditions of the high plains. the blizzard. This cold air is