2
<br />oats, 5,000 acres; and potatoes, 5,000 acres. Lettuce is
<br />grown on about 500 to 1,000 acres in most years.
<br />Climate
<br />Summers are warm or hot in most valleys and much
<br />cooler in the mountains. Winters are cold in the moun-
<br />tains. Valleys are colder than the lower slopes of adja-
<br />cent mountains because of cold air drainage. Precipita,
<br />tion occurs in the mountains throughout the year, and a
<br />deep snowpack accumulates during winter. Snowmelt
<br />usually supplies much more water than can be used for
<br />agriculture in the county. In valleys, precipitation in
<br />summer falls as showers; some thunderstorms occur. In
<br />winter the ground is covered with snow much of the
<br />time. Chinook winds, which blow downslope and are
<br />warm and dry, often melt and evaporate the snow.
<br />Table 1 gives data on temperature and precipitation
<br />for the survey area, as recorded at Manassa for the
<br />period 1952 to 1974. Table 2 shows probable dates of
<br />the first freeze in fall and the last freeze in spring. Table
<br />3 provides data on length of the growing season.
<br />In winter the average temperature is 21.6 degrees F,
<br />and the average daily minimum temperature is 4 de-
<br />grees. The lowest temperature on record, which oc-
<br />curred on January 12, 1963, is -34 degrees. In :summer
<br />the average temperature is 61.4 degrees, and the aver-
<br />age daily maximum temperature is 79.6 degrees. The
<br />highest recorded temperature, which occurred on July
<br />13, 1971, is 94 degrees.
<br />Growing degree days, shown in table 1, are equivalent
<br />to "heat units." During the month, growing degree days
<br />accumulate by the amount that the average temperature
<br />each day exceeds a base temperature (40 degrees F).
<br />The normal monthly accumulation is used to schedule
<br />single or successive plantings of a crop between the last
<br />freeze in spring and the first freeze in fall.
<br />Of the total annual precipitation, 5.52 inches, or 71
<br />percent, usually falls in April through September, which
<br />includes the growing season for most crops. In 2 years
<br />out of 10, the rainfall in April through September is less
<br />than 3.95 inches. The heaviest 1-day rainfall during the
<br />period of record was 1.45 inches on August 5, 1954.
<br />There are about 44 thunderstorms each year, 30 of
<br />which occur in summer.
<br />Average seasonal snowfall is 28 inches. The greatest
<br />snow depth at any one time during the period of record
<br />was 11 inches. On the average, 4 days have at least 1
<br />inch of snow on the ground, but the number of such
<br />days varies greatly from year to year.
<br />The average relative humidity in midafternoon in spring
<br />is less than 35 percent; during the rest of the year it is
<br />about 45 percent. Humidity is higher at night, and the
<br />average at dawn is about 77 percent. The percentage of
<br />possible sunshine is 77 in summer and 73 in winter. The
<br />prevailing wind is from the south-southeast. Average
<br />windspeed is highest, 10.4 miles per hour, in April.
<br />SOIL SURVEY
<br />Climatic data in this section were specially prepared
<br />for the Soil Conservation Service by the National Climat-
<br />ic Center, Asheville, North Carolina.
<br />How this survey was made
<br />Soil scientists made this survey to learn what kinds of
<br />soil are in the survey area, where they are, and how they
<br />can be used. The soil scientists went into the area know-
<br />ing they likely would locate many soils they already knew
<br />something about and perhaps identify some they had
<br />never seen before. They observed the steepness, length,
<br />and shape of slopes; the size of streams and the general
<br />pattern of drainage; the kinds of native plants or crops;
<br />the kinds of rock; and many facts about the soils. They
<br />dug many holes to expose soil profiles. A profile is the
<br />sequence of natural layers, or horizons, in a soil; it ex-
<br />tends from the surface down into the parent material,
<br />which has been changed very little by leaching or by the
<br />action of plant roots.
<br />The soil scientists recorded the characteristics of the
<br />profiles they studied, and they compared those profiles
<br />with others in counties nearby and in places more dis-
<br />tant. Thus, through correlation, they classified and
<br />named the soils according to nationwide, uniform proce-
<br />dures (14).
<br />After a guide for classifying and naming the soils was
<br />worked out, the soil scientists drew the boundaries of the
<br />individual soils on aerial photographs. These photo-
<br />graphs show woodlands, buildings, field borders, roads,
<br />and other details that help in drawing boundaries accu-
<br />rately. The soil map at the back of this publication was
<br />prepared from aerial photographs.
<br />The areas shown on a soil map are called soil map
<br />units. Some map units are made up of one kind of soil,
<br />others are made up of two or more kinds of soil, and a
<br />few have little or no soil material at all. Map units are
<br />discussed in the sections "General soil map for broad
<br />land use planning" and "Soil maps for detailed plan-
<br />ning."
<br />While a soil survey is in progress, samples of soils are
<br />taken as needed for laboratory measurements and for
<br />engineering tests. The soils are field tested, and interpre-
<br />tations of their behavior are modified as necessary
<br />during the course of the survey. New interpretations are
<br />added to meet local needs, mainly through field observa-
<br />tions of different kinds of soil in different uses under
<br />different levels of management. Also, data are assem-
<br />bled from other sources, such as test results, records,
<br />field experience, and information available from State
<br />and local specialists. For example, data on crop yields
<br />under defined practices are assembled from farm rec-
<br />ords and from field or plot experiments on the same
<br />kinds of soil.
<br />But only part of a soil survey is done when the soils
<br />have been named, described, interpreted, and delineated
<br />on aerial photographs and when the laboratory data and
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