As of yesterday, when my 9-year-old and I were hiking in Zion up to Angel's Landing (5,790 feet above sea level), there was no snow, no ice, and no trace of snow or ice anywhere we hiked nor any of the backcountry visible from on top. It was usually 35F lows and 70F high until some clouds came in keeping the night warmer (46F) and the day cooler (64F). 48F and blowing 20 mph, gusting to 30 mph was brisk in t-shirt and shorts even with the workout of climbing up the chained portion, but we weren't up there very long. For any long run in the more wind-exposed stretches, one would want at least wind pants and a puffy or fleece torso layer. Most people had twice that much on.
The Virgin River flow through the Zion Narrows was pretty low - about 55-60 cfs - but cold, maybe 42F. I did okay in fleece socks in trail shoes, but neoprene booties would have been nicer.
Happy Trails, guys!