First of all, its best to put your cham outside in either a cage or plant/tree in a pot. I wouldnt let him climb on any tree in fear that he would run away. Unless the tree is really small and your sure you can get him/her out of it and that it's not toxic (check safe plant list). Furthermore, do not put the cham on the ground, no no, they are arboreal and need to be high in the trees. Sunshine is great for your cham at any age as long as there over a month or two, and 92 degrees isn't too hot for a veiled but make sure the cham has plenty of shade.
You should either have a perch for him, an outdoor cage, or keep constant monitor of his location. I mean..constant. No eyes off the chameleon..ever..or he's gone.
92 degrees is fine. Give him a sprinkler shower if the time outside is extended.
Keep an eye on him nevertheless. I bring mine outside and give him a plant to perch on, or he'll sit on the arm of a lawn chair with me. But once he's gotten a good dose of sun, he wants to be off and exploring. Arboreal or not, they'll march across the ground. I'll let mine climb trees to 4-5 feet, but keep a constant eye on him and am ready to intercept before he gets out of reach.
I've seen hawks get unsuspecting birds from my feeders and I also have a few Great Blue Herons and Sandhill Cranes visit my backyard and pick off Anoles and Geckos from my bushes and fence.
So if my guys go out, it will be in a cage. And even then I have to keep an eye out for Fire Ants.
well im in new jersey and i only have to worry about hawks but i will be there constantly so that should scare them away... also ill just bring out his largest ficus tree and let him perch on that, come june.