天気が良かったので、私たちはピクニックに行った。

weather; the elements; fair weather; fine weather

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

good; excellent; fine; nice; pleasant; agreeable; sufficient (can be used to turn down an offer); ready; prepared; profitable (e.g. deal, business offer, etc.); beneficial; OK

that being the case; because of ...; the reason is ....; given that...

we; us

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

picnic

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to go; to move (in a direction or towards a specific location); to head (towards); to be transported (towards); to reach; to proceed; to take place; to pass through; to come and go; to walk; to die; to pass away; to do (in a specific way); to stream; to flow; to continue; to have an orgasm; to come; to cum; to trip; to get high; to have a drug-induced hallucination