The Climate of Oregon Climate Zone 7 South Central Area

Transcription

1 /65 '5 Unbound issue tqc; Does not circulate (i.13 Special Report 919 May The Climate of Oregon Climate Zone 7 Property of OREGON STATE UNIVERSITY Library Serials Corvallis, OR Agricultural Experiment Station Oregon State University

2 For additional copies of this publication, write: George Taylor State Climatologist Strand Agriculture Hall 326 Oregon State University Corvallis, OR

3 The Climate of Oregon Climate Zone 7 George H. Taylor, State Climatologist Alexi Bartlett Oregon State University Corvallis, Oregon March,

4 Oregon Climate Zone Summary Zone 7 -- 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. 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. Figure 1 is a map showing estimated isopleths of annual precipitation in Zone 7 based on normals (Taylor, Daly, and Gibson, 1992). High elevation points can easily be spotted, since they correspond to high annual precipitation amounts. Rho. Dam i Mathes 0 Merolla? OGthidY 0 aces Shang Prineville Redmond Rend Ohfiteltell 0 Chroviii Sala a minx Beet rn Statics Drowsey 0 O lhothers Burna WSOI AP Squaw Rum Ero Stet 0 Oe Ranch 0 Mathew Refuge HDQ WSO Station Klamath Falls Chiloquin Sprague River 1"" Malin Paisley Le *mew 0 OAd.l Alkali Lake 1 OP ranch Refuge 0 Hart Mountain Refuge White horse Renck Andrews Weston Mine

5 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 maxima are followed by a steady decrease, with lowest monthly averages in midsummer. Farther east, however, springsummer 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 2 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. Median dates of low temperature thresholds in spring and fall are listed in Table 3, and Table 4 gives the length of the growing season at each station.

6 Oregon Climate Zone 7 Table 1. Monthly and Annual Precipitation (inches) Means Name Elevation (feet) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Adel Lake Alkali Lake Andrew Weston Mine Barnes Bend Brothers Burns Chiloquin Dayville Double Drewsey Fossil Grizzly Hart Mountain Refuge Keno Klamath Falls Madras Malheur Malin Metolius Mitchell Ochoco Ranch P Ranch Refuge Paisley Paulina Pelton Dam Prineville Redmond Sisters Sprague River Squaw Butte Whitehorse Ranch

7 Oregon Climate Zone 7 Table 2. Monthly Temperatures ( F) Means Station Code Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Adel Lake Mean Maximum Mean Minimum Monthly Mean Alkali Lake Mean Maximum Mean Minimum Monthly Mean Andrew Weston Mine Mean Maximum Mean Minimum Monthly Mean Barnes Mean Maximum Mean Minimum Monthly Mean Bend Mean Maximum Mean Minimum Monthly Mean Brothers Mean Maximum Mean Minimum Monthly Mean Burns Mean Maximum Mean Minimum Monthly Mean Chiloquin Mean Maximum Mean Minimum Monthly Mean Dayville Mean Maximum Mean Minimum Monthly Mean Double 0 Mean Maximum Mean Minimum Monthly Mean Drewsey Mean Maximum Mean Minimum Monthly Mean Fossil Mean Maximum Mean Minimum Monthly Mean Grizzly Mean Maximum Mean Minimum Monthly Mean Hart Mtn Refuge Mean Maximum Mean Minimum Monthly Mean Keno Mean Maximum Mean Minimum Monthly Mean

8 Table 2. Cont. Station Code Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann - Klamath Falls Mean Maximum Mean Minimum Monthly Mean Madras Mean Maximum Mean Minimum Monthly Mean _ Malheur Mean Maximum Mean Minimum Monthly Mean Malin Mean Maximum Mean Minimum Monthly Mean Metolius Mean Maximum Mean Minimum Monthly Mean Mitchell Mean Maximum Mean Minimum Monthly Mean Ochoco Ranch Mean Maximum Mean Minimum Monthly Mean P Ranch Refuge Mean Maximum Mean Minimum Monthly Mean Paisley Mean Maximum Mean Minimum Monthly Mean Paulina Mean Maximum Mean Minimum Monthly Mean Pelton Dam Mean Maximum Mean Minimum Monthly Mean Prineville Mean Maximum Mean Minimum Monthly Mean Redmond Mean Maximum Mean Minimum Monthly Mean Sisters Mean Maximum Mean Minimum Monthly Mean Sprague River Mean Maximum Mean Minimum Monthly Mean Squaw Butte Mean Maximum Mean Minimum Monthly Mean

9 Oregon Climate Zone 7 Table 3. Median Frost Dates Means Median Dates of Last Occurrence in Spring of Median Dates of First Occurrence in Fall of Station 24 F 28 F 32 F 36 F 24 F 28 F 32 F 36 F Adel 22-Apr 6-May 1-Jun 7-Jun 17-Oct 4-Oct 17-Sep 10-Sep Alkali Lake 12-May 25-May 18-Jun 8-Jul 2-Oct 12-Sep 3-Sep 19-Aug Andrew Weston Mine 13-Apr 6-May 16-May 6-Jun 8-Nov 28-Oct 7-Oct 26-Sep Barnes STN 14-May 4-Jun 28-Jun 16-Jul 30-Sep 11-Sep 2-Sep 15-Aug Bend 13-May 1-Jun 6-Jul 16-Jul 4-Oct 15-Sep 4-Sep 20-Aug Brothers 25-Jun 11-Jul 21-Jul 25-Jul 8-Sep 16-Aug 8-Aug 4-Aug Burns WSO 1-May 21-May 6-Jun 29-Jun 7-Oct 22-Sep 16-Sep 27-Aug Drewsey 10-May 22-May 22-Jun 2-Jul 26-Sep 14-Sep 3-Sep 20-Aug Fossil 5-May 24-May 8-Jun 10-Jul 9-Oct 2-Oct 11-Sep 26-Aug Grizzly 20-May 8-Jun 9-Jul 22-Jul 4-Oct 15-Sep 28-Aug 6-Aug Hart Mountain Refuge 31-May 21-Jun 7-Jul 19-Jul 21-Sep 11-Sep 23-Aug 14-Aug Klamath Falls 2 SSW 29-Apr 19-May 6-Jun 29-Jun 22-Oct 6-Oct 20-Sep 9-Sep Lakeview 29-Apr 17-May 3-Jun 29-Jun 14-Oct 4-Oct 20-Sep 29-Aug Madras 2-May 22-May 7-Jun 2-Jul 6-Oct 1-Oct 10-Sep 1-Sep Malheur Refuge 30-Apr 14-May 1-Jun 28-Jun 2-Oct 19-Sep 5-Sep 27-Aug Malin 2-May 20-May 11-Jun 30-Jun 27-Oct 3-Oct 21-Sep 3-Sep Metolius 4-May 23-May 8-Jun 7-Jul 14-Oct 28-Sep 11-Sep 24-Aug Mitchell 2 NW 10-Apr 4-May 24-May 3-Jun 28-Oct 16-Oct 30-Sep 16-Sep Ochoco Ranger STN. 20-May 20-Jun 11-Jul 26-Jul 2-Oct 8-Sep 15-Aug 2-Aug 00 Ranch 30-Apr 21-May 10-Jun 28-Jun 4-Oct 21-Sep 10-Sep 29-Aug Paisley 1-May 15-May 6-Jun 30-Jun 14-Oct 23-Sep 9-Sep 31-Aug Paulina 21-May 8-Jun 3-Jul 22-Jul 17-Sep 8-Sep 23-Aug 9-Aug P Ranch Refuge 28-Apr 16-May 3-Jun 1-Jul 25-Sep 12-Sep 3-Sep 19-Aug Redmond FAA AP 8-May 29-May 28-Jun 10-Jul 13-Oct 24-Sep 9-Sep 19-Aug Sisters 23-May 29-Jun 14-Jul 26-Jul 18-Sep 8-Sep 17-Aug 4-Aug Sprague River 28-May 25-Jun 12-Jul 22-Jul 17-Sep 30-Aug 18-Aug 3-Aug Squaw Butte Exp. Stn. 6-May 25-May 27-Jun 2-Jul 17-Oct 6-Oct 12-Sep 2-Sep Suntex 16-May 8-Jun 3-Jul 13-Jul 22-Sep 10-Sep 27-Aug 15-Aug Whitehorse Ranch 4-May 19-May 8-Jun 28-Jun 9-Oct 25-Sep 16-Sep 8-Sep

10 Oregon Climate Zone 7 Table 4. Growing Season Means Average Days Between Occurrences of Station 24 F 28 F 32 F 36 F Adel Alkali Lake Andrew Weston Mine Barnes STN Bend Brothers Bums WSO Drewsey Fossil Grizzly Hart Mountain Refuge Klamath Falls 2 SSW Lakeview Madras Malheur Refuge Malin Metolius Mitchell 2 NW Ochoco Ranger STN Ranch Paisley Paulina P Ranch Refuge Redmond FAA AP Sisters Spaque River Squaw Butte Exp. Stn Suntex Whitehorse Ranch