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<br /> <br /> <br />Community Wildfire Protection Plan 19 September 2018 <br />3.5.2 Climate and Temperature <br />As is typical of areas in the lee of large coastal mountain ranges, the Yakima River Basin is generally <br />arid. Precipitation varies with elevation and distance from the Cascades, from 150 inches annually at <br />the Cascade crest to 10 inches at the Columbia River. Disparities in precipitation rates from one area <br />to another affect runoff rates and the character of rivers in different drainages, which influence <br />flooding and land-use potential. Summers in Kittitas County tend to be dry; approximately two-thirds <br />of the county’s precipitation occurs between October and April, with much in the form of snow. In <br />the winter, considerable snow often accumulates in the higher elevations. In the Kittitas Valley, snow <br />season generally ranges from November through February, with significant variation from one <br />season to the next. <br /> <br />Because of the variation in elevation, temperatures vary greatly in the Yakima River Basin. In the Kittitas <br />Valley, summers tend to be hot, with wide divergent fluctuations, and mild to severe winters. Data <br />are scarce for higher elevations; however, those areas are generally characterized by cool summers <br />and cold winters. For example, in the Subalpine Fir forest zone, which extends from approximately <br />2,000 feet to the timberline, mean July temperatures in the range of 55ºF to 65ºF can be expected. <br />3.5.2.1 Wind <br />During the summer, pressure is higher on the western side of the Cascades and lower over the <br />heated basin of eastern Washington, with the pressure difference increasing during the day as <br />temperatures soar over eastern Washington. Air accelerates from high to low pressure and it finds <br />the weakest location called Stampede Gap, where the terrain is only 3,000 to 4,000 feet high. Air <br />accelerates through the gap and spreads out over the Kittitas Valley, with northwest winds on many <br />summer days gusting to 30 to 40 miles per hour (Mass 2009). <br />The prevailing wind is from the northwest. The daily wind speed averages 8 to 10 miles per hour in <br />the spring and summer, although wind speeds up to 20 to 30 miles per hour are not uncommon in <br />the Kittitas Valley. <br />Kittitas County Conservation District