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Show The tables below can be used to obtain the mean dates of occurrence of the last spring freeze and the first fall freeze. Values obtained from table # 1 are mean dates of occurrence; that is, 50 percent of the years the freeze will occur earlier, and 50 percent later than shown. Table # 2 is used to obtain dates that correspond to other probability levels. The average freeze date is selected from the map and the factor corresponding to the desired probability level is obtained from the table. TABLE # 1 Relations among the mean lengths of the freeze- free seasons and the mean occurrance dates for the last freeze in the spring and the first freeze in the fall. Mean length Mean dates of occurrance of 32 F- free for freezing temperature season ( interpolated Last 32 F ir i First 32 F in from map) the spring the : fall days date dat( a 0 July 24 July 24 10 July 19 July 29 20 July 14 Aug 3 30 July 9 Aug 8 40 July 4 Aug 13 50 June 29 Aug 18 60 June 24 Aug 23 70 June 19 Aug 28 80 June 14 Sep 2 90 June 9 Sep 7 100 June 4 Sep 12 110 May 30 Sep 17 120 May 25 Sep 22 130 May 20 Sep 27 140 May 15 Oct 2 150 May 10 Oct 7 160 May 5 Oct 12 170 Apr 30 Oct 17 180 Apr 25 Oct 22 190 Apr 20 Oct 27 200 Apr 15 Nov 1 210 Apr 10 Nov 6 220 Apr 5 Nov 11 230 Mar 31 Nov 16 TABLE # 2 Factors for converting mean freeze dates ( 50% probability) to other probability levels. Factors to be added to mean Probability dates of occurrence leve1 Spring Fall % days days 5 26 - 21 10 20 - 16 15 16 - 13 20 13 - 11 25 11 - 9 30 8 - 7 35 6 - 5 40 4 - 3 45 2 - 1 50 0 0 55 - 2 1 60 - 4 3 65 - 6 5 70 - 8 7 75 - 11 9 80 - 13 11 85 - 16 13 90 - 20 16 95 - 26 21 Interval between isopleths is 20 days. The frost free season in the Uinta Hydrologic Area ranges from less than 20 days in the Uinta Mountains to more than 160 days in the extreme south. Topography The topography of an area affects not only climatic factors but also land use, runoff, and vegetative cover. The Uinta Hydrologic Area is characterized by large variations in topography as can be noted on map # 5. The highest point in the area and also in the State, Kings Peak, is 13,498 feet above aea level. The lowest point, on the Green River at the southern |