What kinds of armour were used in hot/humid climates historically? Plate armour seems like a good way to overheat in places like the middle east, north Africa, and Meso-America. So what did people wear? Chainmail? Lamellar? Padded/quilted armour?
You have to be more specific. What time period are you talking about specifically? Armor and weaponry changed drastically even throughout the middle ages.