The Chesler Park/Joint Trail has some unique rock features and offers great views of the Needles. Plus, it is a short hike, keeping the amount of sun exposure to a minimum.
Arches National Park, UT
Arches NP is a unique park in that all of the points of interest are quite far apart and there aren't too many hiking trails. We decided to do a car tour with minor hiking, and it was nice to be a tourist and just get out of the car to take pictures, since it was so hot. Even though the park is a little out of the way, it is worth the trip to see some rock arches.
Hiking and Rappelling Orderville Canyon — Zion National Park, UT
Navajo Loop, Peekaboo Loop, and Queens Garden - Bryce Canyon NP, UT
Bryce canyon is a relatively small National Park, but if you are in Utah you should definitely make a small side trip to see this unique canyon. There aren't too many trails to choose from, but if you have a couple hours to spare, this easy dayhike is the perfect way to see all the best parts of the canyon up close. The trail is well-maintained with not much elevation change, the only downside is that it is quite exposed, dusty, and can get pretty hot in Utah sun. No matter how long you expect to hike, be sure to bring extra water.