You cannot, mostly because Germans "just don't say it that way".
I think of it in this way: Germans are often very literal, and saying "I am too warm/cold" would be like literally saying you have hyper-/hypothermia (where your body temperature is dangerously high or low). Usually this is not the case - you just want to express that you're a little uncomfortable with the temperature and it's causing you to sweat or shiver (not die). There are also other slang meanings associated with saying things this way, which as a beginner you would want to avoid.
As a result, personal feelings about the temperature are expressed as feelings rather than fact - using the dative personal pronoun ("to me it is too warm").
no, you shouldn't. "Ich bin warm" "I am warm" is little bit ambiguous.^^ "ein warmer Bruder" is a fruit. There's nothing wrong with it, don't get me wrong! But you should know how people could understand it.
best regards Angel
Edit: The same problem with the sentence "ich bin kalt / mir ist kalt". Please have a look here: https://www.duolingo.com/comment/23846327