Page 18 and 19 of the WSG - Dressing for the Weather
Effective temperature = temperature around the character
Personal temperature = temperature of the player, which may vary from the player standing right beside (imagine a desert - one character in plate mail, one in a robe; effective temperature is identical for both, personal temperature may be very different).
Maybe that's why sword and sorcery female warriors wear skimpy armor?
Clothing (attire) can be designed for very cold, cold, moderate and hot effective temperatures. The types of armor also have different effects on personal temperature depending on the effective temperature.
For example using Table 3: Effects of Clothing and Armor on Personal Temperature
Loin cloth in the hot and humid jungle +0 addition to effective temperature to calculate personal temperature.
Plate mail in the hot and humid jungle, +30 Fahrenheit.
Though the table only deals with temperature, not humidity effects - believe me it is complex enough. Exertion adds heat.
A player may find themselves in too much or too little clothing, leading to being unprotected (I can't believe I am writing this).
Provided the player's personal temperature is between 21 - 79 F, all is good. Fall outside that boundary and Str, Dex, Con, Land movement and attack rolls can be modified. Not sure what this has to do with protected and unprotected as is stated on page 19, that being protected reduces chance of suffering damage as a direct result of exposure to temperature.
Ah, that's many tables forward in Table 9, page 26, damage from heat and cold.
Ok in the jungle in plate mail, and it's 100F, personal temp +30 = 130. Fighting for 6 turns = +5 F = 135F total. That's hot.
I am Personal temp > 120F therefore Str -2 no exertion, -4 exertion; Dex -1/-3, Con -4/-5; Land move 1/2, Attack -4.
I am wearing metal armor in an effective temperature > 80F = UNPROTECTED.
DM must make a Con check at +6 every 3 turns (assume on modified con), or I suffer 1-6 damage (max 10% current HP)! 10% rule must be else normal men would die like flies in heat and cold - hey isn't that what happened to Napoleon's army?
If I am higher level I can modify the Con check, e.g. at 4th level by -1.
These lost hit points may kill me but if I survive, I can regain these HP at a rate on 1 per hour; if I can get my temp into a tolerable range.
Wow - is this clunky or what.
For everyday play - no way.
But if venturing to Tatooine or Hoth - yes these tables might be a resource the DM could avail themselves PRIOR TO GAMEPLAY.