そっちの天気は？

that way (direction distant from the speaker, close to the listener); there (place distant from the speaker, close to the listener); that one (something close to the listener); you; your family; your company; that person (someone close to the listener)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

weather; the elements; fair weather; fine weather

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis