Setting them up outside requires a lot of care (or luck). You need to put the aviary in a position which allows them to warm up (north-facing aspects are ideal) but also allows them a cool retreat (underground retreats are good for most lizards and some snakes, but you must ensure they won't flood). If you know what you're doing iIt's definitely possible to keep reptiles well outside of their natural range without any problems, but if you don't know what you're doing you'll probably cook or freeze them even within their natural range. Some things (such as, say, Lace Monitors or many skinks) are far tougher than other things (such as tropical pythons).