1983-04-26_PERMIT FILE - M1983067 (7)

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CLI}LATE • The climate of Adams County is that of the semiarid high plains . It is modified by the Rocky Mountains to the west and the higher country of the Black Forest area to the south . The effects of the mountains vary considerably with increasing distance from the western end of the county toward the east . The county , 72 miles long and 13 miles wide , ranges in eleva- tion from S , S70 feet at the southwest corner to 4 , S00 feet at the north-east corner , and is within a plains climate that changes rapidly to a foothills climate just west of the county. Many features of the climate at Denver , which is represent - ative of the extreme western and southwestern part of Adams County , can be applied with some modification to the entire county . Variations in climate from the western border eastward include increased averae windspeed because of the reduced effectiveness of mountain shielding , slightly lower average annual precipitation , lower amounts of precipitation and snow- fall in winter and early in spring , increased amounts and variability of summer precipitation , greater average variation in daily and annual temperatures , and somewhat lower cloudiness and higher percentage of sunshine on an annual average . Table 9 gives climatic data compiled from records kept mainly at Byers , Arapahoe County , Colorado . These data are representative of most of Adams County . The average annual temperature is near 50' at an elevation • of S , 200 feet , but this can be expected to vary a few degrees from the lower elevations at the eastern end of the county to the higher elevations at the western end . The wide average range in daily temperature of 25' to 35' and a wide average range in annual temperature are typical of the High Plains . As a result of wide variations from day to day or over a period of a few days , extremely hot weather in summer or extremely cold weather in winter is generally of short duration and is followed by ;'101-0 moderate temperature . The average annual growing season in Adams County is about 130 days . Table 10 gives the orohabiLity at Byers , Arapahoe County , of the last frceain- temperatures in spring and the first Eree -- in. temperatures in fall . Data for long periods indicate that the average annual precipitation in the county ranges From L2 . S to L4. 5 inches . It tends to be higher in the western part . Variations within the county are related to the local terrain , elevation , and slope . Particularly in spring and summer , the extreme variability i.n the amount of precipitation from year to year and bets:reen localities in the same year is so large than even long - period averages are affected by chance occurrences and are not easiLy interpreted in terms of actual climatic differences . Probable annual precipitation (fig . L9) is particularly signiEicant in • showing the expected variation of rainfall From year to year .