During the summer, this area of Zion National Park [1] can be extremely hot, and in the early spring, it's often too muddy to hike. Trails in this area head north from Highway 9 west of the town of Springdale [2] and are accessible without paying the park entrance fee.
From the parking area on Highway 9, this trail heads 2.5 miles up Huber Wash, through painted desert and canyons. One of the highlights of hiking in this area, besides the desert scenery, is the abundance of petrified wood. There's even a logjam of petrified wood at the 2.5-mile mark, where the trail ends in a box canyon, decked with a hanging garden.
If you're up to a tricky climb over the petrified logjam, you can climb up and catch the Chinle Trail, then hike five miles back to the road on that trail. The Chinle Trail emerges onto Highway 9 about 2.5 miles east of the Huber Wash Trailhead.
During the summer, this area of the park can be extremely hot, and in the early spring, it's often too muddy to hike. Thus, this is the ideal autumn hike. Even then, it'll be quite warm. Remember to bring plenty of water.
The Huber Wash Trailhead is about six miles west of the park entrance on Highway 9, near a power substation. Because the trail starts outside the park, it's not necessary to pay the park entrance fee if all you want to do is hike in this area.
Links:
[1] http://www.moon.com/destinations/utah/zion-and-bryce/zion-national-park
[2] http://www.moon.com/destinations/utah/zion-and-bryce/springdale