Obviously most people enjoy a clear, low humidity day vs a hot, muggy day. How were these differences described in the ancient world? How would an ancient Greek historian have characterized a hot, sticky muggy day vs a clear day or was weather discussion limited to rain/no rain?
A quick look found:
From Book 19 of Homer’s Iliad:
From an Orphic Hymn 82 to Notus (god of the South Wind):
“Humid” shows up in Aristophanes’ works, also, but he was a pretty bawdy fellow, so I won’t quote. His usage does appear to mean wet and warm.
While these are taken from latter day translations to English, obviously they had a word or words that meant something similar to humid.
“Non calor sed umor est qui nobis incommodat.”
Sorry, I had to do it. 
Forsooth, thine armpits raineth.
Sultry!
I remember at least one occasion where Aristophanes used the word “humid” to mean moist… he really wasn’t a shy guy.