Henninger Flats is a 6 mile out and back trail near Pasadena that climbs steadily through the San Gabriel Mountains. The trail follows a fire road the entire way, which means it’s wide enough for comfortable hiking but also means you’re exposed to direct sun for most of the journey. Dogs need to stay leashed throughout, so plan accordingly if your dog isn’t used to that level of constraint on a longer hike.

The main drawback here is the lack of shade on the fire road itself. Summer hikes can feel brutal—the pavement absorbs and radiates heat, and there’s nowhere to duck out of the sun. If you’re going in warm months, get an early start before 8 am and bring significantly more water than you’d think necessary. The effort pays off, though. After a rain or on a windy day, the views of the LA basin are genuinely impressive. On clear days you can see out toward the coast, and the perspective really shifts once you understand how high you’ve climbed.

When you reach the flats themselves, the landscape changes noticeably. Trees provide actual shade, which feels like a relief after the exposed fire road. There’s a nature center up there, along with picnic tables scattered around if you want to rest and let your dog recover from the climb. The area is a working research station, so it maintains a quieter, less crowded feel than some other local hiking spots.

A public campground is also available if you’re interested in staying overnight. The trail is rated moderate, which feels accurate—the 6 miles isn’t extreme in distance, but the steady uphill grind and elevation gain mean it’s not a casual stroll either. Most hikers take 2-3 hours to summit. The fire road surface is consistent and stable, though it can get dusty, so be prepared for your dog to need a good rinse afterward.