Why do you have so many verbs for being, such as Estar, Ser, and Tener? forget my ass.
Estar and ser are probably the most common verbs to get mixed up.
Both verbs mean 'to be.' The difference is in the tense. Estar refers more to temporary condition, while ser is somewhat "permanent," or long-lasting. You would use estar to say 'it's cold,' or 'está frío'. But the question still remains, "Why use estar when ser means the same exact thing? Plus, you used it's, and that's a contraction with the word is."
Temperature can obviously change. You may feel cold one moment, and suddenly warm the next. But
SwordCard's is a much better explanation, as he's likely taken Spanish 4 already.