Grant County lies in the eastern central part of Oregon along the Strawberry Range. It is within both Climate Division 7 (South Central Oregon) and Climate Division 8 (Northeast Oregon) established by the National Climatic Data Center. Below is a description of the climate of Division 7 and 8 followed by specific descriptions of Grant County. Climate tables for various parameters, as observed at long-term climate stations in Grant County, are included below.

Climate Division 7 — South Central Oregon

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 1961-1990 period. Figure 2 shows the Grant 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.

Tables 2a and 2b lists the average number of days with precipitation amounts exceeding certain thresholds.

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.

Tables 5 and 6 list median frost dates and mean growing seasons, respectively, for four different temperature thresholds.

Table 7 and 8 list average monthly and annual heating and growing degree days, respectively.

Climate Division 8 -- Northeast Oregon

Climate Zone 8 occupies the northeastern corner of Oregon, occupying all of Wallowa, Baker, and Union Counties as well as portions of Umatilla and Grant. The area includes several sizable mountain ranges with large valleys between them. Among the larger cities are La Grande, Baker City, John Day, and Enterprise, although the biggest of these (La Grande) has a population of only slightly above 10,000 residents.

Several million acres of Federal land are being utilized by ranchers for livestock which is the major industry in this region. Beef cattle are the main livestock raised, but sheep, dairy herds, poultry, and hogs are significant income sources as well. Field crops are also an important commodity and include wheat, potatoes, barley, oats, and grass seed. Lumber is also produced in significant quantities from the forested areas in the region.

Annual precipitation totals in Zone 8 valley areas are generally below 20 inches. Some locations surrounded by high mountains, such as Baker City and Unity, barely exceed 10 inches per year. High elevation sites, on the other hand, receive much larger annual totals. Locations near the top of the Wallowa Mountains, for example, may exceed 100 inches precipitation per year, much of it in the form of snow. Figure 1 shows NOAA climate stations in Zone 8, which were in operation during the 1961-1990 period. Figure 2 shows the Grant County region from the Oregon annual precipitation map. Table 1 lists monthly and annual normal precipitation at Zone 8 sites. Highest normal precipitation totals tend to be in winter and late spring. Unlike most of Oregon, Zone 8's monthly distribution in comparison is remarkably uniform throughout the year. Tables 2a and 2b list the average number of days with precipitation amounts exceeding certain thresholds.

Zone 8's distance from the ocean causes its annual temperature variations to be rather large. Table 3 lists normal monthly temperatures at stations in the area. Mean maximum temperatures are mostly in the 80's in summer months and in the 30's in winter. The dry, clear summer days are usually followed by cool nights; nighttime lows generally average in the 40's. The coldest temperatures in the region (and probably in the state) are observed in Seneca, located in a deep valley surrounded by mountain ridges. January low temperatures in Seneca average a cold 8.4 deg F. Annually, Seneca experiences an average of 22 days with below-zero temperatures. Seneca is in a tie for the coldest temperature ever recorded in Oregon, -54 deg F, set in February 1933.

Table 4 lists average monthly and annual snowfall totals for various stations.

Tables 5 and 6 list median frost dates and mean growing seasons, respectively, for four different temperature thresholds. While some of the lower valley sites have fairly long growing seasons, a few of the colder locations have very short seasons. At Seneca, Austin, and Ukiah, the mean length of time between freezing temperatures is less than six weeks.

Tables 7 and 8 list average monthly and annual heating and growing degree days, respectively.

County Description

Established: Oct. 14, 1864
Population: 7,800
Area: 4,528 sq. mi.
Economy: Forest products, agriculture, hunting, livestock and recreation.
County Seat: Canyon City

Grant County was created in 1864 from Wasco and Umatilla Counties and was named for Gen. Ulysses S. Grant. It shares boundaries with more counties (eight) than any other county in Oregon. Grant County contains the headwaters of the John Day River, which has more miles of Wild and Scenic designation than any other river in the United States. More than 60 percent of the land in the county is in public ownership.

Climate Tables (Grant County, Oregon)