This popular Seattle-area waterfall hike has its own hydroelectric plant, and by August it’s noticeably thinner

Twin Falls sits about 35 miles east of Seattle off I-90, and it’s one of the most dependable short hikes in the state — waterfalls, old growth, and a bridge over a canyon, all in under three miles round trip. Here’s what most people don’t know until they’re standing there wondering why the falls look smaller than the photos: there’s a small hydroelectric plant built right into the waterfall, quietly taking some of the water for itself.

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A trio of falls in one short hike

The hike starts at the Twin Falls Trailhead in Olallie State Park, a little over 2 miles round trip with about 500 feet of climbing — easy enough for a first family hike, with just enough stairs to make you feel like you earned it. We hiked it on a weekday morning and had long stretches of the old-growth section nearly to ourselves, which almost never happens on a trail this close to Seattle.

You’ll pass a massive old-growth tree the trail calls the Big Tree, then descend 104 steps to the best view of the Lower Falls, a 150-foot drop that’s worth every one of those steps on the way back up. A little farther, a bridge crosses the canyon with views of the Upper Falls upstream and the Lower Falls below — technically three separate cascades, all grouped together as Twin Falls.

The power plant hiding at the falls

What you won’t see from the trail is the small run-of-the-river hydroelectric project diverting water just upstream. For roughly three months most summers, the South Fork Snoqualmie’s flow drops so low the plant can’t even generate power, and the rest of the time the diversion still pulls enough water that the falls visibly thin out.

My honest take: go in spring or early summer if you want the waterfall from the postcard. By August you’ll still get a solid hike and a decent view — just don’t expect the thundering version everyone’s posting in May.

What to know before you go

Park at the Twin Falls Trailhead off I-90 Exit 34, and bring a Washington Discover Pass ($10 for the day, $45 annual) — this is Olallie State Park land, and rangers do check. Dogs are welcome on leash, there’s a bathroom at the trailhead, and the trail’s easy enough that most families won’t need trekking poles.

The trail hasn’t always been this forgiving. A 2006 flood sent the South Fork surging to roughly 9,000 cubic feet per second and wiped out the riverside path entirely, and a 2014 flood did more damage before crews rebuilt the route around a slide in 2016 — look for the undercut banks and driftwood piled well above the current waterline if you want to see the evidence.

Want more than the falls? Keep going past the bridge and the trail climbs about another mile to meet the Palouse to Cascades Trail, dropping you at the Homestead Valley Trailhead if you’ve got a second car waiting. We’ve got the full mile-by-mile breakdown of the trail if you want more detail before you go.

Twin Falls proves you don’t need a full day off to feel like you left the city behind — just pick your season wisely. Have you hiked it before the water dropped, or after?

Trip tips: grab a rental car to make the drive out easy, or lock in a hotel nearby if you’re turning it into a weekend in the Cascades.

Rules and fees change — always confirm current requirements before you go.

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