In English it's quite common (and idiomatic) to say "I am too warm" when you actually mean "I feel too warm". Your body temperature is probably perfectly fine - you might just be starting to sweat to maintain it, and you'd rather not.

Typical overly-logical German, on the other hand, makes that distinction mandatory. To say mir ist (es) zu warm you're literally saying "it is too warm to me". Saying the sentence with ich bin... will get you funny looks, because it's not said that way in German.