"In the South it is warm, and in the North it is cold."
Translation:На юге тепло, а на севере - холодно.
You may have found your answer by now, given the age of your comment, but а introduces a second clause which contrasts the first. (Which, by the way, did not make me happy when I got this sentence to translate from Russian to English, used "but" instead of "and", and was marked wrong.)
Right - и is exclusively "and". This and that. Mom and Dad. Apple pie and ice cream. "А" indicates more of a distinction, which could be either "but" or "and". It is dark at night and/but it is light during the day. Or the example here, where either and or but could work (although I'd say there's a little more stress on the contrast if "but" is used).
Why is the dash not used in the first half of the sentence, «на юге тепло» but it is used in «на севере - холодно»?