Yes, they say "Ektachrome transparency" in blue lettering on the mount, and "Kodachrome transparency" in red.

Except for attics, temperatures here are pretty moderate. Indoor air is pretty dry due to heating, summers are humid, but not anything close to that of the south U.S.
Air conditioning is not common. Things like this often get stuffed into basements, which would be a pretty constant 50 - 70 degrees (F) and moderate humidity.
But I'm only guessing at the conditions these slides enjoyed.