I'm going into winter now but I ran most of my rigs on the back verandah over summer, blew them out with some air once a month.
Daytime temperatures in summer here go over 40C regularly
with cgminer, undevolting and downclocking memory my cards still ran at acceptable temps (under 85C at peak temp for day)
A *lot* of miners have rigs in garages, sheds or barns.
oh and I dont use cases