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<br />•. <br />Climate <br />Exhibit K <br />The climate of the mining area is of a semiarid, continental type. <br />Winters are cold and relatively dry. Summers are characterized with <br />wide variations in daytime and night temperatures. Annual precipitations <br />ranges about 20 inches which is about 8 inches more than Longmont and 1z <br />inches more than Boulder. Relative humidity is about 30 - 35 percent in <br />summer and about 40 - 50 percent in the winter. Winter temperatures are <br />modified by the frequent occurance of warm downslope winds from the west. <br />Eleven sites in the Boulder area were selected for soil temperature <br />measurements. These sites ranged in elevation from 5,230 feet to 8,120 <br />feet. Mean annual soil temperatures calculated from measurements at a <br />depth of 20" ranged from 53.1° at 5,230 elevation to 4404° at 8,120 feet. <br />Rased on this a decrease of 0.3° can be expected for a increase of 100' <br />elevation. <br />In Longmont swmner temperature reaches 100° about 1 year in 2; and in <br />Boulder, about 1 year in 3. The average July temperature at Boulder is <br />73.6°, but at Longmont is only 71.6°. These temperatures are accompanied <br />by 1°w humidity and therefore, are more confortable than might be expected. <br />Alsc, high daytime temperatures are followed by cool evenings and by nights <br />usually below 60°. <br />The length of the growing season in Longmont is 140 days and in Boulder <br />it is 148 days. At Longmont the average date of the first killing frost in <br />fall is :;eptember 28; at Boulder it is October 4. The average date of the <br />• last killing frost in spring is May 11 at Longmont and May 9 at Boulder <br />