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<br />Perhaps the most significant factor affecting the <br />climate is the remoteness of the basin from the distant <br />source areas of the air masses. This means that the air <br />masses have to cross wide land areas before they reach <br />the basin. In crossing these areas they leave Illllch of <br />their available precipitation, and their air temperatures <br />are changed considerably by radiation from the land <br />surface. <br />Primarily because of its mid continental location. the <br />basin experiences weather that is known for its tluctua. <br />tions ~nd extremes. Also there are variations between <br />areas within the basin. Winters are relatively long and <br />cold over much of the basin, while summers are fair and <br />hot. Spring is cool, moist and windy; autumn is cool, dry <br />and sunny. Averages are misleading for seldom does <br />"average" weather actually occur. Instead, weather tends <br />to tluctuate widely around the annual averages, with the <br /> <br />occurrence and the ~egree of the fluctuations being <br />unpredictable. Thus the climatic averages have to be <br />thought of as generalizations of the more common <br />occurrences over a period of time. <br />As shown in figure 4, average annual precipitation <br />varies from over 40 inches in parts of the Rocky <br />Mountains and southeastern parts of the basin, to as low <br />as 6 to 12 inches immediately east of the Rocky <br />Mountains. Complicating the annLlal variations, there is a <br />wide variation in the basinwide pattern of monthly <br />precipitation. Figure 5 shows the monthly distribution <br />of precipitation for four representalive locations within <br />the basin. <br />Precipitation received from November through March <br />generally is in the form of snowfall. Thunderstorms are <br />prevalent in July and August and often are localized. <br />with high-intensity rainfalL Prolonged droughts and <br /> <br />FIGURE 4 <br />AVERAGE ANNUAL TOTAL PRECIPITATION <br /> <br /> <br />\/ <br />-~ <br /> <br />LEGEMll <br /> <br />.lnOW'~I.CIES <br /> <br />D,ZTO,IIICNES <br /> <br />D"Tozu,lcNEs <br /> <br />COLORADO <br /> <br />.nTOIlOIICHEI <br /> <br />.0vnllOl.C~[' <br /> <br />OHI USED 01 'HIOD 1111-10410 <br /> <br />12 <br /> <br />'I <br /> <br />~ <br /> <br />~ <br /> <br />. <br /> <br />I <br /> <br />SC'L[''''.'CC.CCC <br />C 'cc <br /> <br />.....C,,~.fE suLl ," ."". <br /> <br />MINNESOTA <br /> <br />. <br />;; <br />. <br />s"". III <br /> <br />I KANSAS <br />. I <br />i ---1'------------1 OURI <br />~I L_~~~~.. <br /> <br />i\ <br />