| Three Sisters Wilderness | |
|---|---|
 Aerial view of the wilderness, showing Middle Sister (left) and South Sister | |
 Interactive map of Three Sisters Wilderness | |
| Location | Lane /Deschutes counties,Oregon,USA |
| Nearest city | Sisters, OR (20 miles NE) Bend, OR (20 miles E) |
| Coordinates | 44°05′N121°57′W / 44.083°N 121.950°W /44.083; -121.950 |
| Area | 286,708 acres (1,160.27 km2) |
| Established | September 3, 1964 (date of official designation under theWilderness Act)[1] |
| Governing body | U.S. Forest Service |
TheThree Sisters Wilderness is awilderness area in theCascade Range, within theWillamette andDeschutes National Forests inOregon, United States. It comprises 286,708 acres (1,160.27 km2), making it the second-largest wilderness area in Oregon, after theEagle Cap Wilderness. It was established by theUnited States Congress in 1964 and is named for theThree Sisters volcanoes. The wilderness boundary encloses the Three Sisters as well asBroken Top, which is southeast of South Sister.[2]
Three Sisters was designated as aUNESCO Biosphere Reserve under theMan and the Biosphere Programme in 1976, and was one of 17 reserves in the United States withdrawn from the programme in June 2017.[3][4][5]
Oregon Route 242 separates the Three Sisters Wilderness from theMount Washington Wilderness to the north, while theWaldo Lake Wilderness shares the southern boundary.[2]
The three peaks were known by pioneers as Faith, Hope and Charity.[6] Nearby landmarks include The Husband, The Wife, and the Little Brother.[7]
Many types of landforms make up the wilderness area, but the most common arevolcanic features, the most notable being the Cascades which arestratovolcanoes having formed around 1.6 million years ago.[8] Numerouscinder cones have formed on their flanks as well as manylava flows that contain hundreds oflava tubes.[9]
The Three Sisters Wilderness ranges in elevation from 2,000 to 10,363 feet (610 to 3,159 m). The Three Sisters—North Sister at 10,090 feet (3,075 m), Middle Sister at 10,052 feet (3,064 m), and South Sister at 10,363 feet (3,159 m) — are found in the eastern portion of the Wilderness. IncludingBroken Top—just to the south at 9,175 feet (2,797 m) — there are 14 glaciers offering one of the best examples of the effects ofglaciation in the Pacific Northwest.Collier Glacier, between North and Middle Sister, is the largestglacier in Oregon.[2] The headwaters of theWild and ScenicWhychus Creek (formerly Squaw Creek[10]) emerge in the Wilderness.[2]
| Climate data for South Sister 44.1007 N, 121.7698 W, Elevation: 9,825 ft (2,995 m) (1991–2020 normals) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Mean daily maximum °F (°C) | 26.5 (−3.1) | 25.8 (−3.4) | 27.0 (−2.8) | 30.5 (−0.8) | 39.2 (4.0) | 46.7 (8.2) | 57.8 (14.3) | 57.8 (14.3) | 52.7 (11.5) | 42.1 (5.6) | 30.3 (−0.9) | 25.5 (−3.6) | 38.5 (3.6) |
| Daily mean °F (°C) | 20.4 (−6.4) | 18.4 (−7.6) | 18.7 (−7.4) | 21.1 (−6.1) | 28.5 (−1.9) | 35.3 (1.8) | 44.7 (7.1) | 44.8 (7.1) | 40.2 (4.6) | 32.0 (0.0) | 23.8 (−4.6) | 19.6 (−6.9) | 29.0 (−1.7) |
| Mean daily minimum °F (°C) | 14.3 (−9.8) | 11.0 (−11.7) | 10.3 (−12.1) | 11.6 (−11.3) | 17.9 (−7.8) | 23.9 (−4.5) | 31.7 (−0.2) | 31.8 (−0.1) | 27.7 (−2.4) | 21.8 (−5.7) | 17.2 (−8.2) | 13.7 (−10.2) | 19.4 (−7.0) |
| Averageprecipitation inches (mm) | 20.23 (514) | 14.71 (374) | 16.25 (413) | 13.2 (340) | 9.05 (230) | 5.67 (144) | 1.45 (37) | 1.63 (41) | 4.37 (111) | 11.19 (284) | 19.24 (489) | 23.2 (590) | 140.19 (3,567) |
| Source: PRISM Climate Group[11] | |||||||||||||
Forest cover in the Three Sisters Wilderness includesDouglas fir,Pacific silver fir,subalpine fir,mountain hemlock,western hemlock,lodgepole pine andponderosa pine. A large area of the wilderness abovetimberline containsalpine meadows.[12]
Popular recreational activities in the Three Sisters Wilderness include camping, hiking, climbing and fishing. South Sister and Middle Sister are not technically difficult climbs, but summiting North Sister requires technical expertise and equipment. More than 260 miles (420 km) of trails cross the wilderness, including 40 miles (64 km) of thePacific Crest Trail.[12] The 9.8-mile (15.8 km)French Pete Trail and its surrounding old-growth forest, a nationwide political issue in the 1970s, are located on the western edge of the wilderness nearCougar Reservoir.[13]
To find the table data on the PRISM website, start by clickingCoordinates (underLocation); copyLatitude andLongitude figures from top of table; clickZoom to location; clickPrecipitation, Minimum temp, Mean temp, Maximum temp; click30-year normals, 1991-2020; click800m; clickRetrieve Time Series button.
