Location and surroundings
South Twin lies in Whatcom County, Washington, in the United States, and belongs to the Twin Sisters subrange of the Skagit Range in the North Cascades. It is part of the broader Cascade Range, itself within the Pacific Coast Ranges of the North American Cordillera. At 2,123 m, it is the highest of the 40 named peaks in the Twin Sisters and the high point of that range. The mountain rises above a landscape of steep ridges, forested lower slopes, and alpine terrain higher up.
Neighbouring peaks
- Twin Sisters (peak), 1,710 m, 0.5 km NW
- North Twin (peak), 2,024 m, 1.4 km NW
- Twin Sisters Mountain (peak), 1,757 m, 3.8 km SE
- Bear Mountain (peak), 1,283 m, 5.5 km SW
- Bald Mountain (peak), 1,391 m, 6.7 km SW
- New York Mountain (peak), 1,310 m, 6.9 km SW
- Bowman Mountain (peak), 1,019 m, 8.5 km NW
- Miner Mountain (peak), 1,285 m, 8.8 km S
These neighbours show how central South Twin is in the Twin Sisters group: it is higher than all of the listed nearby peaks, including North Twin, which is the closest summit above 2,000 m.
The view from the summit
Within 25 km, the highest peaks are led by Mount Baker at 3,287 m, about 15.0 km NE. Other high points in view or near view include Colfax Peak at 2,851 m to the NE and Hadley Peak at 2,291 m, also to the NE. Closer by, Crag View lies 14.2 km E at 2,133 m, while Skookum Peak is only 0.6 km SE away at 2,018 m. Skyline Divide is another nearby high ridge, 18.0 km NE.
The range
South Twin belongs to the Twin Sisters, whose high point is South Twin itself. The range contains 40 named peaks, and South Twin ranks first by elevation among them. The Twin Sisters are part of the Skagit Range in the North Cascades, within the larger Cascade Range of the United States. In this setting, South Twin is the main summit of a compact mountain group rather than a separate isolated peak.
Climate and weather
Climate figures for the summit are estimates from NASA POWER climate data for 2001–2020. The warmest month is August, at about 7 °C, and the coldest is December, at about -6 °C. Mean temperatures are above freezing at the summit from May through October. The surrounding area receives about 2,050 mm of precipitation a year; November is the wettest month at about 320 mm, and July the driest at about 35 mm. Expect wet weather, cloud, and rapid changes typical of the North Cascades.
Best time to visit
For a summit at 2,123 m, the most practical window is usually the period when temperatures are above freezing and snow cover is more manageable. Here that means May to October, with the warmest conditions in August. The drier part of the year is around July, while late autumn is much wetter. Even in the warmer months, expect cool mornings, wind, and lingering snow patches on higher ground, so clothing and footwear should match alpine conditions.
Nature and wildlife
The mountain sits in a North Cascades landscape of dense lower forest, steep rocky slopes, and alpine ridges higher up. At this elevation, vegetation thins quickly into subalpine and alpine plants, with open ground, heather, grasses, and scattered krummholz where conditions allow. Wildlife in the region can include deer, black bear, mountain goats, and a range of birds adapted to forest and high-country terrain. Seasonal snow, wet ground, and exposed rock are part of the normal environment on and around South Twin.
Guides and organised ascents
For a mountain like South Twin, a certified guide is usually worth considering if you are unfamiliar with steep alpine terrain, route-finding, or early-season snow. In the United States, the national mountain guide association is the American Mountain Guides Association, an IFMGA/UIAGM member, and the national alpine club is the American Alpine Club. Examples of established guiding companies in the country include RMI Expeditions in Ashford, Washington, and Exum Mountain Guides in Moose, Wyoming. Guided trips typically depend on the number of days, group size, hut nights, and equipment needs.
Safety and preparation
South Twin’s height, weather, and terrain call for mountain clothing, navigation skills, and the ability to handle wet rock, snow, and sudden visibility changes. The North Cascades are known for fast weather shifts and slippery surfaces after rain or snowmelt. Carry enough food, insulation, and water, and be prepared to turn back if conditions worsen. For mountain rescue in the United States, the emergency number is 911; dispatchers alert the local search and rescue team, usually run by the county sheriff or a national park.
Interesting facts
South Twin is the highest of 40 named peaks in the Twin Sisters and the high point of that range. Its nearest higher major summit in the wider area is Mount Baker, 15.0 km to the NE. The mountain sits in Whatcom County in northwestern Washington, within the North Cascades. Nearby North Twin is close in distance but lower, which makes South Twin the dominant summit of the group.
FAQ
How high is South Twin? South Twin rises to 2,123 m.
Where is South Twin? It is in Whatcom County, Washington, in the United States, within the Twin Sisters of the North Cascades.
What range is South Twin part of? It belongs to the Twin Sisters, within the Skagit Range, Cascade Range, and North American Cordillera.
What are the nearest peaks? The closest listed summit is Twin Sisters, 0.5 km NW, followed by North Twin at 1.4 km NW.
Is there water on the way to South Twin? The mountain is in a wet alpine region, but you should plan to carry your own water. On a day outing, 1.5-3 litres is a sensible amount depending on heat and length; snowmelt may be available in season, but it should be treated.
How is South Twin compared with nearby peaks? It is higher than the nearby North Twin and the other listed neighbours, and it is the highest peak in the Twin Sisters.
What is the mobile phone coverage like? Coverage in the hills is patchy and depends on the operator. On open ridges it may be better, while in valleys and behind ridges it often fails. Always download maps before setting out, and remember that 112 reaches emergency services over any available network.