Worm Flows, Winter Climbing Route

Area Status: Open
Winter Climb2

The Worm Flows Climbing Route is the primary route used by climbers during the winter and early spring to reach Mount St Helens Summit. Worm Flows is the most direct route to the summit of Mount St. Helens during the winter season. Ice axe, crampons, and avalanche awareness are recommended on this route. Skis with climbing skins or snow shoes with cleats are also highly recommended.

From the Marble Mountain Sno-Park use the Swift Ski Trail, #244 to reach timberline. Cross to the west side of Swift Creek, just above Chocolate Falls (elev. 3,700'). Follow ridges and open slopes to the crater rim. Wooden route marking posts guide climbers from timberline to approximately 4,800' elevation. Round trip is approximately 12 miles, Round trip time is approximately 7 to 10 hours. To reduce your exposure to avalanche potential, stay away from snow loaded slopes and gully bottoms. Stay off the cornices at the crater rim.

Climbers should be prepared for winter climbing conditions. Sign in at the register and sign out on your return.

 Two websites to help plan your trip are: Northwest Avalance Center West Slopes South and Mountain-Forecast.com.

Mount St. Helens Climbing information.

At a Glance

Current Conditions: 11/21/2023: Road 83 is passable to all vehicles up to Marble Mountain Sno-Park. SnoPark Passes are required at Marble Mountain beginning December 1st. Ice is present on the climbing route above the tree line. Ice axes and crampsons are strongly recommended. Be mindful of glissade trails leading you off the climbing route.
  • Safety Alert: A cornice (giant, overhanging mass of snow) forms every year at the summit and can release at any time, plunging into the crater. Stay well back from the edge and don't trust footprints you see. 
  • Pack out your trash, please. Please bring your own blue bags due to limited supply at the trailhead.
  • Please do not congregate at the summit or in the parking lot.
Reservations: Between April 1 & Nov. 30 climbing permits are limited in number and purchased online in advance.  
Permit Info: Mount St. Helens Climbing Permits are required year-round for each person and each day they will be traveling above 4800 ft elevation on the slopes of Mount St. Helens.
  • April 1- Nov. 30: Climbing permits are limited and must be purchased online in advance at Recreation.gov. Permits will be released one month at at time for purchase
  • December 1- March 31: Permits are free and available at the Marble Mountain Sno-Park kiosk.
Washington State Sno-Park Permit required December 1 to March 31. Permits not available on-site. Purchase in advance or from a vendor. No other pass required during Sno-Park season
Usage: Medium
Best Season: Winter/Early Spring
Busiest Season: Winter/ Early Spring
Restrictions: Snowmobiles are restricted in the Non-motorized zone, the climbing areas between Monitor Ridge and the Worm Flows.
Closest Towns: Cougar, WA
Water: No
Restroom: Vault Toilets at Marble Mountain Sno-Park
Information Center:

General Information


From Cougar, WA drive east on Lewis River Road, which turns into Forest Road 90. Continue on Forest Road 90 until the intersection with Forest Road 83. Turn left on Forest Road 83 and continue approximately 6 miles to the Marble Mountain Sno-Park. During the winter and early spring Forest Road 83 is gated at the Sno-Park.

General Notes:

Know Before You Go:

Some Cornices (overhanging snow) on the Crater Rim of Mount St. Helens are unstable and prone to sudden failure. Extreme caution is advised! Do not approach the crater rim unless you can find a wind-scoured area where the surface of the rim is visible. The crater rim is unstable and is subject to frequent rockfall and collapse.

Stay back from the crater edge, it is potentially hazardous at any time of year (especially during the period of elevated avalanche danger and rockfall during the spring thaw).

Winter/early Spring Climbing Tips from a Mountain Steward.

Climbing Preparation and Safety Information

  • Climbing Safety
  • Climbing Essentials
  • Active Volcano Hazards
  • Hypothermia/Altitude Sickness


Weekends can be busy.


Mountain Climbing

Related Information

Recreation Areas

Recreation Activities


  Elevation : 
2,800 ft. - 8,364 ft