Zion has some really special places. Many of them are well known, like Angel's Landing, Observaton Point, and the three Emerald Pools.
Taste of Zion and Sights in Zion are a couple videos I've shot so far of these hikes.
Fortunately on my days off, I can eat a good breakfast in the employee dining room, take a bottle of water and light pack, and hike to these really great views.
I always recommend an early start. Its cooler, less crowded, and
you have the entire day to enjoy it.
Also, you can avoid the afternoon thunderstorms, although rare, can occur in late summer.