Well behaved dogs can be off leash. There are existing fire pits at the lake (please use). Often, other backpackers will be around - beneficial if you're not ready to enter Idaho's expansive wilderness with just your own group/family. 9 miles roundtrip. Elevation Gain: 1950 feet.
Perhaps one of the best beginner-esque lake hikes closest to Boise, making your way to Jennie Lake can either be packed-in overnight or and out-and-back day hike. You'll be delighted by the secluded ambiance of the lake and the cool mountain breeze rushing through the pines.
Getting There:
Make your way to the Jennie Lake trailhead by heading north on Hwy 21 (from Boise) past Idaho City but before Lowman. About 10 to 15 miles after Idaho City you'll see signs for Whoop-Um-Up recreation area, which directly after you'll turn right onto 384 and then eventually take the fork left to 348. This road seems to be maintained and suitable for most sedans (...maybe not a Prius). After 7 miles after the fork, look for a sign that says "Jennie Lake trail". Searching Google Maps "Jennie Lake Trailhead" will navigate you via exact directions to the trailhead, which is a quaint 5-6 car gravel parking.
From there, the trail is quite obvious, starting at ~5,900 ft and ascending essentially the entire way to the lake. Plan 3 to 4 hours for the ascent along a well marked, dirt and gravel trail (about 4 1/2 miles). You'll see wildflowers, pine, deer, a mint field, and a small river.