Thunderbolt Ski Trail

The Thunderbolt Trail is the historic expert ski trail on the east side of Mount Greylock, built by the Civilian Conservation Corps in the 1930s. It starts at Greylock Glen in Adams. In winter, when it's covered in snow, it's for skiing and skinning only, with no hiking up or down. In summer, only the lower section is open to hikers; DCR has closed the upper section to hiking to control erosion.

Hikers who want the summit from this side use the Bellows Pipe Trail instead. Here's what's open, when, and the trail's place in the mountain's history.

A CCC Ski Trail

DCR's history notes credit the Civilian Conservation Corps with building the "expert class" Thunderbolt Ski Trail and the Thunderbolt Shelter, alongside Bascom Lodge and the rebuilt Rockwell Road. The CCC's 107th Company was based on the mountain from 1933 to 1941. DCR's own hike guide calls it "the famed Thunderbolt Ski Trail."

Skiing the Thunderbolt

There's no lift. Skiers climb on skins and ski down. DCR's winter trail map marks it as an expert ski trail. Greylock Glen's trail rules say that when the trail is snow-covered, it's ski and skin use only, and hiking up or down isn't allowed.

The Glen's site links a Thunderbolt ski patrol map from the National Ski Patrol's western Massachusetts region, and points volunteers to the Thunderbolt Ski Runners, the local group that helps maintain trails on the Glen and the reservation. The Glen's photos include the Thunderbolt Ski Race.

This is backcountry skiing on a trail DCR marks expert. Check conditions before you go.

Hiking the Thunderbolt

• Lower section: from Thiel Road at Greylock Glen to the Bellows Pipe Trail, 0.9 miles, moderate.
• To the summit: continue on the Bellows Pipe Trail, 2.6 miles in all from Thiel Road, aggressive.
• Upper section: closed to hiking to control erosion. DCR asks hikers to use the Bellows Pipe Trail to reach the Appalachian Trail.

Greylock Glen describes the trail as very strenuous: rocky double track at first, then a wide ski trail covered in ferns. Its hiking access is from the Glen's Bellows South Trail.

DCR's Bellows Pipe and Ragged Mountain Hike

The easiest way to see the Thunderbolt on foot is DCR's hike 7. From 175 Gould Road in Adams, it follows old ski trails, including part of the Thunderbolt, to a view on Ragged Mountain: 5 miles, about 4 hours, 1,288 feet of climb, moderate to strenuous. It returns down the Thunderbolt for 0.5 miles before rejoining the Bellows Pipe Trail. More in our hiking guide.

Other Winter Options

DCR's winter trail map shows snowshoe and backcountry ski trails, plowed and unplowed roads, and snowmobile trails. Greylock Glen's trails are open for snowshoeing and cross-country skiing. The Bradley Farm Trail at the visitor center is an easy cross-country ski loop.

Good For / Maybe Skip If

• Good for: expert backcountry skiers, history fans, and hikers doing the Bellows Pipe and Ragged Mountain loop.
• Maybe skip if: you want an easy summit hike. Take the Cheshire Harbor Trail.
• Maybe skip if: it's snow-covered and you're on foot. Hiking isn't allowed on it then.

Trail closures are posted on the DCR park page.