Yeah heat/cold becomes much less problematic as your tech increases/ gals get more experienced. Baseline Heat and cold dmg is actually rather small. Most early outfits actually have a significant penalty in order to make you feel the effects. Sometimes more then double or triple. But the more advanced outfits start to get back towards baseline(100%).
Also because heat inflicts stun and cold saps stamina, the more HP a gal has the more regen of both they possess. A meaty gal in decent gear will rarely notice the effects even in prolonged battles.
Aside from the very heavy non powered armor, like platemail, environment damage stops being a factor in most battles after the mid game.