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<br />E7-'[IIBIT K -CLIMATE <br />1.0 INTRODUCTION <br />The azea known as Dowe Flats is located in the eastern foothills of the Rocky Mountains (elevation <br />5340') about three km east of Lyons, Colorado. In general, the area can be classified as having a <br />continental climate. Being far removed from any moisture sources, the area experiences an abundance <br />of sunny weather. The relative lack of atmospheric moisture often results in lazge diurnal temperature <br />cycles. Large annual temperature cycles result from seasonal variations in solar elevation angle as well <br />as a lack of atmospheric moisture. These characteristics are somewhat modified by the proximity of the <br />Rocky Mountains. The mountains act as a thunderstorm growth region during the spring and summer <br />so that Dowe Flats may receive more precipitation than a typical continental location. Mountain Chinook <br />wind events often influence diurnal temperature differences during the winter and many winter-time daily <br />maximum temperatures above 60°F have been recorded. Also, the gradual increase in terrain elevations <br />near the mountains tend to block the area from shallow arctic air masses which often penetrate the plains <br />region to the east during the winter. <br />Specific weather data for a climatologically significant period of record aze not available for Dowe Flats. <br />However, a climatological record is available for the Waterdale substation located approximately 17 km <br />• to the north of Dowe Flats. Waterdale occupies a similar foothills location (elevation 5230') and is near <br />enough that the data should be applicable for a climatological evaluation of Dowe Flats. The period of <br />record at Waterdale is 1931 - 1989 and includes temperature, precipitation and freeze data. These <br />parameters, as well as wind speed and direction, will be discussed further in the following sections. <br />2.0 TEMPERATURE DATA <br />Table 1 lists several temperature statistics for the Waterdale station including monthly mean maximum, <br />monthly mean minimum, monthly mean average, monthly highest and monthly lowest temperatures. The <br />extreme high and low temperatures on record are 104°F and -34°F respectively. The annual mean <br />maximum temperature is 63.6°F, while the annual mean minimum is 33.0°F. The annual average <br />temperature is 48.3°F. On average, the warmest month is July, while the coldest is January. <br />3.0 FREEZE DATA <br />Freezing temperatures may occur ten months out of the yeaz. July and August are the only months never <br />to record a temperature below 32°F. Annually, the area experiences about 22 days on which the <br />maximum temperature does not exceed freezing. The minimum temperature reaches 32°F or less about <br />172 days per year, on average. The length of the growing season is moderate. Table 2 lists the probable <br />dates of the last spring freeze and the first fall freeze. There is a 5096 probability that the last spring <br />• freeze will occur on or before May 14 and that the first fall freeze will occur on or after September 27. <br />