Trillium Lake sits at about 3,600 feet in the Mount Hood National Forest, a couple of miles south of US 26 near Government Camp and roughly forty miles southeast of Portland. It covers 63 acres and it is shallow, which is the reason it swims well: by late July the top of the water column is genuinely warm, unusual for a Cascade lake at this elevation. The day use area is at the dam on the northeast side, with a boat ramp, an accessible fishing pier, vault toilets and a paved lot. Day use parking is $10 per vehicle.

The view is the reason most people come. Mount Hood stands almost due north of the lake and on a still morning the whole mountain lands upside down on the surface. It is one of the most photographed views in the state, and the boardwalk section of the Trillium Loop Trail on the south shore is where the tripods line up before sunrise. The loop is about two miles, mostly flat, partly boardwalk across marshy ground, and easy with kids.

Swimming is unsupervised. Most people get in off the grassy bank near the day use area or off the boardwalk on the far side, and the bottom is soft and silty rather than rocky. Motors are not allowed, so the water stays flat and quiet for swimming, paddling and fly fishing from a float tube. There is a second boat ramp inside the campground. The lake is stocked with rainbow trout and gets steady fishing pressure all summer.

Trillium Lake Campground has single sites at $26 and doubles at $50, and the 2026 season runs roughly May 22 through October 31, with reservations through recreation.gov. A group day use area is $72 and the amphitheater rents for $90. Snow closes the road in winter. From November 1 through April 30 the access road becomes a groomed route for skiing, snowshoeing and snowmobiling, and you need an Oregon Sno-Park permit to park at the highway end.

Everything is close here. Government Camp with food and gas is five minutes north, Timberline Lodge is fifteen minutes up the mountain, and the Pacific Crest Trail crosses US 26 nearby. Mirror Lake and Little Zigzag Falls are short hikes in the same stretch of highway. Because of the proximity to Portland the day use lot fills early on summer weekends, and the Forest Service closes the gate when it does, so arriving before ten or after four is the practical advice.