Difficultly: At worst, class 3 on the main trail.
Distance: Round trip - 12.4 miles.
Elevation gain: About 5000 feet.

Tallest-Youngest-Highest-Largest. These are just a few of the words that describe South Sister and some of it's features.
It is the tallest of the Three Sisters, outdistancing both Middle Sister and North Sister. As well as being the third tallest mountain in the state of Oregon.
It is the youngest, geologically speaking having the most recent volcanic activity of the Three Sisters.
Highest describes the lake that sits right near the summit, Teardrop Pool, being the highest lake in Oregon.
Lastly, largest describes Prouty Glacier, holding the distinction for the largest glacier in Oregon.

To the North, awesome views of the neighboring Sisters await you at the summit. To the Southeast, Broken Top, Mount Bachelor, and Green Lakes are visible. Even Mount Hood, Mount Adams, and Mount Thielsen may be visible on a clear day.

Getting There

Starting from Bend, drive west on the Cascade Lakes Highway for 27 miles. Continue past the Mt. Bachelor Ski Area 6.5 miles. Then turn left at Devils Lake Campground. The sign for the South Sisters Trail head is at the end of the campground parking lot, just to the right of the restrooms. The trail pointer is labeled "South Sister Climbers Trail 36."

Red Tape

A Northwest Forest Pass permit is required to park at the trailhead. The permits cost $5 per car for a day pass. Annual passes are available for $30 and are good for all national forests in Oregon and Washington. The passes are available at most Forest Service offices and outdoor stores in the area. Permits, which are free, are required to enter the wilderness. These can be filled out at the trailhead. A maximum group size of 12 people are allowed in the Three Sisters Wilderness.

To purchase your permit online, click here

When To Climb

Summer & Autumn:South Sister has one popular route that can be climbed with little technical skill or equipment during the summer. This is the south side route and starts from either Green Lakes or Devils Lake. The route requires only descent physical conditioning and a tolerance for massive amounts of scree. There is also another class 4 route ascending between the Lewis Glacier and Prouty Glacier that offers snowfields and small waterfalls during the summer while avoiding the crowds as well as the dusty, rotten scree route mentioned above. However, this route does not follow a well-worn trail as the Southern route does.

Other routes exist that offer more technical challenges. The east side routes include the Prouty Glacier and the Prouty Headwall. From Middle Sister, climbers can take the North Ridge, Silver Couloir, or the North Face Couloir.

Winter & Spring:South Sister can be done during the Winter and Spring. Snowshoes can be used in some instances but Ice axe and crampons are highly recommended as well as knowing how to properly use them. If there is a cloud covering the summit, it is highly recommended to just give up as you will probably be climbing in some very adverse conditions.

Avalanche preparedness and safety are also recommended on climbing this peak in the Winter and Spring. It is a good idea to bring a snow shovel and know how to use it, as well as having prior experience with checking avalanche conditions. An avalanche beacon would also be a worthwhle investement if climbing with someone else or with a group.

Click here for the Northwest Avalanche Center webpage.

Camping

Camping is permitted at the trail head at the Devils Lake Campgound.

Geology & Glaciers

South Sister is the youngest (geologically speaking) and the tallest of the Three Sisters and is said to have last erupted about 1900 years ago. It's main cone is primarily made up of andesite, dacite, and rhyodacite.

Interestingly there has been some uplift in the past years as well as swarms of earthquakes, none of which are too active currently. The uplift is located about 3 miles West of South Sister and covers an area of about 9-12 miles. The uplift is only about 4 inches but has been detectible with satellite imagery.

Click here for a link to the current seismicity.

South Sister is home to 8 Glaciers, one of which is the largest known glacier in the state of Oregon. That one being Prouty Glacier, which covers about 1.1 square kilometers

Other glaciers on South Sister are:
Carver Glacier
Clark Glacier
Eugene Glacier - Which now covers an area of about 0.09 square kilometers.
Irving Glacier
Lewis Glacier - Which now covers an area of about 0.3 square kilometers.
Lost Creek Glacier
Prouty Glacier (as previously mentioned) - Covering 1.1 square kilometers.
Skinner Glacier