2017-11-29_PERMIT FILE - C1981010 (2)

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s The daily surface temperature near Craig can vary by 30°(F) or more, even in the winter months (Stearns-Roger, 1973). As the average temperatures indi- cate, summer days are usually warm, but seldom hot. Summer nights are gener- ally cool, especially if accompanied by night (downs lope) breezes. Tempera- tures above 95°F (35°C) only occurred in 8 months during the 30 years from 1936 to 1965 (Berry, 1966). Since 1977 however, temperatures above 95°F have been recorded in 2 of the 31 months. During the twenty-three year period (1951-1973) the average maximum temperatures for summer months did not reach 90°F (32.2°C) (Table 2.1-15). Winter months are usually cold, but the average daily maximum temperature for January, historically the coldest month, has been above freezing in more than half of the years of record. This results in a high frequency of winter days warm enough to melt off the snow cover. Winter nights are usually co 1d. The temperatures often drop rapidly once the sun begins [o set. Most of the win- ter days are more comfortable because of the low humidity and the usual amounts of bright sunshine (solar insolation) for the region (Table 2.1-16). The normal diurnal and annual temperature cycles for the Craig vicinity are presented in Figures 2.1-15 and 2.1-16 respectively. If they are compared with Figures 2.1-17 and 2.1-18, the usual inverse relationship between temper- ature and relative humidity can be noted. Likewise, relative humidity differs conversely with hourly and monthly temperature maximums. For example, [he highest humidity occurs at S:OOam (MST) when temperatures are the lowest and the lowest (R. H.) is recorded around 2:OOpm (MST). Stearns-Roger (1973) cal- culated the monthly average for relative humidity to fall between 43 and 89 percent. Hourly averages range between 35 and 86 percent with a mean of 60.6 percent. 2-49