Hot Homeland (3.5e Trait)
From D&D Wiki
Your were born and raised in hot equatorial regions, and your body has become attuned to heat as a result.
Benefit: You gain a +2 bonus on Fortitude saves against environmental heat effects. Additionally, you gain fire resistance 1.
Drawback: You take a -4 penalty on Fortitude saves against environmental cold effects. Additionally, all Cold-based spells and attacks do 2 extra points of damage to you.
Special: This trait must be taken at 1st level if it is to be taken at all. You may not select this trait if you have a permanent immunity to cold for any reason. If you select this trait and later gain a permanent immunity to cold, you lost the benefits of this trait.
Roleplaying Ideas: Your character is entirely comfortable in weather that makes everyone else sweat. On the other hand, you shiver in weather that everyone else finds pleasant. Your character background should mention where you were born and raised.