Don't use freezing cold NS. Even if it didn't freeze, if it were below 0 deg. Centigrade it could freeze other stuff, like your pt. Some meds might start to precipitate, ask a pharmacist, they love being treated like professionals instead of vicodin dispensers.
I've used units sitting overnight in sub-zero; we had frozen condensation in the unit's built in O2 lines, battery operated stuff was sluggish, and a naugahyde (vinyl) seat cover cracked when pushed on as I was climbing in. Tape adhesive doesn't want to work. Blankets were cold even after the air in the unit had warmed up. BVM's did not want to conform.
High storage temps for shelf items, generally eighty deg F is the threshold, and I believe it shortens shelflife to keep them anywhere near that hot. A car in direct sun can get to 130 deg F. Tape adhesive becomes problematic. Long enough, and paper wrappers on sterile dressings get brittle. Latex can get brown and brittle in time, including valve flaps on masks, gloves.
Had enough?