Muscle Armor effectiveness

[Flavivs Aetivs]

The Battles of Adrianopolis and Chalons were both fought at Midday (No clue for the first one, latter one began around 2:30). It could easily have been 90 degrees Farenheit Daniel (admittedly though France is significantly cooler than SC).

If you stay hydrated and keep your head ventillated then heavy armour is no problem at all.

Exactly

I don't know how someone would wear full metal armor in 115 F + climate without getting burnt.

Armor, helmet, and greave liners. We found lots of them at Dura.

By the way what tunic do you wear? Is it such a Persian tunic which gets lots of air through?

Depends. I have a linen, light wool, and heavy wool tunic and have no problem with any of them during the summer, unless I'm wearing Braccae/Feminalia.