Chasm Lake via Longs Peak Trail Hiking Guide
Chasm Lake sits in a cirque directly beneath Longs Peak, the park's highest summit, about four miles and more than 2,000 vertical feet above the Longs Peak Trailhead. Much of the route is above treeline, and the lake itself is alpine. Here is what the climb asks of you, when to start, and what fall conditions look like.
Permit: Rocky Mountain National Park requires an entrance pass at every hour of the year: $30 per private vehicle for one day or $35 for 7 days, $25 or $30 per motorcycle, $15 or $20 per person on foot or bike (16 and older), the $70 park annual pass, or an America the Beautiful pass. Non-US residents 16 and older pay an extra $100 each unless entering on an annual or America the Beautiful pass. Entrance stations take cards only. From late May to mid-October you also need a Timed Entry reservation to enter the park between 9 a.m. and 2 p.m. (May 22 to October 12 in 2026), even at the Longs Peak Trailhead; it costs a $2 Recreation.gov fee per vehicle, and you print it for the dashboard. No permit is needed for the day hike.
The Numbers
AllTrails lists the out-and-back at 8.5 miles with 2,522 feet of gain and calls it hard. The park's trail list gives 4.2 miles one way and 2,360 feet from the Longs Peak Ranger Station, which sits at about 9,300 feet. The trail climbs through forest to treeline, crosses open tundra on the Longs Peak Trail, then turns left at Chasm Junction for the last stretch. There is a privy near that junction.
Start in the Dark
AllTrails notes that many hikers arrive between 3 and 5 a.m., and the trailhead lot fills early. The early start isn't just about parking: the park's Longs Peak report recommends being back to treeline by noon to limit lightning exposure, and storms here can arrive with little warning. Bring a headlamp for the first hour and plan your turnaround time before you leave the car.
Chasm Crossing and the Final Slabs
Between Chasm Junction and Chasm Meadow the trail traverses a steep slope the park calls Chasm Crossing; in the October 4 report it was snow-free and dry. Above the meadow you scramble up rock slabs and a boulder field marked with cairns to reach the lake. The park warns that those slabs are steep, usually wet with runoff, and icing becomes a serious hazard in fall, so poles or traction devices are worth packing.
Fall and Winter on Longs Peak
By early October the park describes the mountain as shifting into winter, with storms bringing hail, sleet and snow, freeze-thaw ice, and rockfall. Wet and cold together can bring on hypothermia quickly, so pack waterproof layers and extra warmth. AllTrails advises against attempting Chasm Lake in winter without mountaineering experience, avalanche training and technical gear.
Fees and Reservations at Longs Peak
The Longs Peak area is an outlying part of the park, about 9 miles from Beaver Meadows Visitor Center plus a mile of side road, but it still needs an entrance pass. Park-wide timed entry covers the 9 a.m. to 2 p.m. window through the summer season into mid-October; most Chasm hikers pull in hours before 9, so they never need it. Display any reservation you do have on the dashboard.
Hiking tips for Chasm Lake via Longs Peak Trail
- Be on the trail before dawn so you're below treeline by noon.
- Pack poles and microspikes in fall for the wet, icy slabs below the lake.
- Download an offline map; AllTrails says cell service is unreliable here.
- Carry a waste bag, as AllTrails suggests, to keep this busy alpine area clean.
- Turn around at the meadow if the slabs are glazed and you lack traction.
Nearby trails to explore
- Ouzel Falls via Wild Basin Trail
- Sky Pond via Glacier Gorge Trail
- Gem Lake Trail (Lumpy Ridge)
Hike this trail with TrailMates
Chasm Lake starts in the dark and ends under Longs Peak, so a partner for the predawn miles helps. Use TrailMates to find Estes Park hikers starting from the Longs Peak Trailhead. Download the TrailMates app to connect.