Deschutes County lies in the central part of Oregon along the eastern side of the Cascades. It is within two different climate divisions, Climate Division 5 (High Plateau) and Climate Division 7 (South Central Oregon) established by the National Climatic Data Center. Below is a description of the climate of Division 5 and 7 followed by specific descriptions of Deschutes County. Climate tables for various parameters, as observed at long-term climate stations in Deschutes County, are included below.
Climate Division 5—High Plateau
Oregon's High Plateau, a region bordered by the Cascades on the west and several minor mountain ranges on the south and east, comprises much of Klamath County and parts of Lake and Deschutes Counties. Due to generally high elevations, the Plateau has cool temperatures and receives a significant amount of snow. Its distance from the coast, coupled with its location downwind of the Cascades, causes its annual precipitation to be lower than in the mountainous areas surrounding it.
The Cascade crest, running north-south at a longitude of about 122deg W, is lower in elevation in the High Plateau than in most parts of Oregon. Only one peak, Mt. Thielsen, exceeds 9,000 feet. As a result, the 'rain shadow' effect produced by the mountains is less dramatic in this zone than in areas to the north. Another notable difference between the High Plateau and the surrounding zones is its average elevation east of the Cascades. Whereas the places east of the northern and central Oregon Cascade peaks are typically 2,000 - 4,000 feet above sea level, the lower elevations of the High Plateau average about 5,500 feet.
As air moves from west to east over the Cascades in Zone 5, it begins to descend; the greater the descent, the drier the air becomes. While air parcels reaching Bend to the north have descended about 4,000 feet from the crest and are usually quite dry, similar air parcels moving into the High Plateau drop only about 2,000 feet. This difference is reflected in the average annual precipitation total for these two areas. Bend receives only about 12 inches per year, while points in the High Plateau receive more than 20 inches.
The remoteness and ruggedness of the High Plateau has resulted in low area population. Only a few small towns, including Chemult, Silver Lake, and Odell Lake, serve as population centers; none exceeds 1,000 residents, however. Primary economic enterprises in the area include tourism (such as Oregon's only national park, Crater Lake), livestock raising (primarily beef cattle and sheep), and agriculture (includes alfalfa hay, grass and legume seed crop, and wheat).
Normal precipitation values in Zone 5 are dependent upon west-east orientation and elevation. Crater Lake, in the west, receives an average of more than 65 inches per year, while Fremont and Summer Lake to the east receive about 12 inches. Crater Lake's elevation is about 2,000 feet higher than the latter stations. Figure 1 shows NOAA climate stations in Zone 5, which were in operation during the 1961-1990 period. Figure 2 shows the Deschutes County region from the Oregon annual precipitation map. Table 1 lists normal monthly and annual precipitation totals at the Zone 5 climate stations. Tables 2a and 2b list the average number of days with precipitation amounts exceeding certain thresholds.
Temperatures in Zone 5 vary considerably during each day and throughout the year. The Crater Lake weather station, highest in elevation, has the coolest temperatures. Average maximum temperatures at this point range from the high 60's in summer to the mid 30's in winter; lows are near 40 deg F in summer and high teens in winter (see Table 3). Summer Lake and Fremont are the warmest sites during the summer, and the latter has the coldest average low temperatures in winter.
The combination of high elevation and distance from the coast can produce cold temperatures in any month of the year for the High Plateau. Table 4 lists average monthly and annual snowfall total for the various stations. Table 5 list median frost dates, respectively for four different temperature thresholds. Table 6 lists the growing season (average number of days between these dates). All Zone 5 sites except Summer Lake have very short seasons (less than 2 months at 32 deg F). With such a short (and highly variable) season, it is little wonder that Zone 5 is not a major Oregon agricultural area.
South Central Oregon, the largest of the Oregon climatic divisions, is a vast area of high desert prairie punctuated by a number of mountain ranges and isolated peaks. This region is predominantly livestock country; in addition to beef cattle, there are large numbers of sheep, dairy herds, horses, and swine. There are large amounts of land under irrigation as well, particularly in the Deschutes, Crook, Jefferson, and Klamath Counties. Among the major field crops grown are potatoes, alfalfa and other hay crops, mint, wheat, oats, barley, and onions. In the remaining counties comprising this zone (Grant, Harney, and Lake), irrigated acreage is much smaller; grazing lands and dry land farming predominate.
Figure 1 shows NOAA climate stations in Zone 7, which were in operation during the 1961-90 period. Figure 2 shows the Deschutes County region from the Oregon annual precipitation map. Most of this region receives relatively low amounts of precipitation. As can be seen in Table 1, most of the stations in Zone 7 receive less than 15 inches per year. However, some of the higher mountain sites receive significantly greater precipitation. For example, Steens Mountain in Harney County, whose summit is more than 9,000 feet above sea level, receives more than 40 inches per year at its higher elevations. Other mountainous locations are also known to receive high annual amounts. Most of the stations in Zone 7 receive their highest monthly precipitation in the winter months with a secondary maximum during late spring and early summer. For other locations, the precipitation is greatest during spring and summer. Stations near the Cascades (such as Sisters, Bend, Chiloquin, Klamath Falls, and Madras) tend to have annual distributions very similar to those in western Oregon: winter maximum are followed by a steady decrease, with lowest monthly averages in midsummer. Farther east, however, spring-summer peaks are much more pronounced. At Hart Mountain, for example, the four wettest months are March through June. The months of July through September are generally the driest of the year throughout the region. These months are characterized by isolated local thunderstorms. Some months are very wet and others almost completely dry.
Table 3 lists normal monthly temperatures for Zone 7 measurement stations. Summers are generally quite warm, although the relatively high elevations tend to moderate the temperatures somewhat. Pelton Dam and Dayville, with mean maximum temperatures in the 90's during the warmest summer months, are the hottest stations in this region. The coldest sites listed are Brothers, Hart Mountain, Sprague River, and Ochoco Ranger Station. It is certain that some of the higher elevations are colder than the areas listed here, however.
Table 4 lists average monthly and annual snowfall total for the various stations.
Established: Dec. 13, 1916
(County information obtained from Oregon Blue Book)
Climate Tables (Deschutes County, Oregon)