LOL! The "correct" way to say "I'm hot" when it's too warm in Spanish is "I have heat", "Tengo calor."Good points above.
In time you´ll get those phrases, that´s why it does help a lot to watch tv in Spanish.
To say "I´m hot" when you feel the temperature is hot in a room or any place, translates as "Estoy caliente" and in many Spanish speaking countries, that could trigger some strange looks, as in some countries that also means...."I´m horny". ,,, so in Spanish you´d usually say "Hace Calor" which is "It´s hot".
In my previous statement I was autocorrected to say "numerous ddifferences" where I meant to say "humorous differences". But as stated, when people realize you are not a native speaker to the area, even if you are fluent, most let it slide or politely correct you if it's inappropriate.