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.