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Ilf III,~~IIII~~~II~ DocDate:12/11/2001 <br />5 ~; 2.04.8 CLIMATOLOGICAL INFORMATION <br />• The climate of the area is characteristic of semiarid steppe regions. <br />Stagnant high-pressure systems often persist over the region for days, their <br />passages being blocked by the Rocky Mountains. This causes an abundance of <br />clear sunny days with large, daily temperature variations. In July, tempera- <br />tures are expected to vary from 81°F average maximum during the day to 44°F <br />average minimum at night. January temperatures vary from an average maximum <br />32°F during the day to an average minimum of 1.4°F at night. The growing season <br />may be anticipated to be from 60 to 70 days. <br />Freeze data for Hayden to the west indicate that the mean date for the last <br />freeze (32°F) occurs on May 27, with the mean date of the first freeze in fall <br />occurring on August 26. The mined area lies some 750 feet in elevation higher <br />and can be expected to have a somewhat shorter frost-free period. Seasonal <br />• variations of air temperatures at Hayden and Steamboat Springs are depicted in <br />Figure 2.04.8-1 (Stule et al, 1979). <br />Wind rose data (Figure 2.04.8-2) obtained from the Hayden power station <br />indicates up-valley flow is prominent, while down-valley flow from the east is <br />more frequent because drainage flow endures for a longer period of the average <br />day and can persist for several days during the winter months. <br />The average wind speed at the Hayden Station is 6.5 mph. Winds of less <br />than 2 mph were considered calm, occurring 18.9 percent of the time. <br />Maximum storm events for a 24-hour period at the area of the mine are esti- <br />mated to be: <br />2 year 1.6 inches <br />10 year 2.0 inches <br />100 year 2.3 inches <br />- 106 - (Rev. 5/86) <br />