Southwest rhymes with:
northwest, addwest, bequest, eastern-west, farwest, key_west, midwest, natwest, northwest, norwest, penwest, quest, request, stateswest, telequest, telewest, west
Southwest sounds like:
saddest, sadist, sawdust, scotched, seduced, sketched, southeast, southgate, southside, southstate, staccato, stacked, staged, stake-out, staked, stakeout, stashed, stateside, stateswest, statist, steketee, sticht, stickiest, stitched, stocked, stockett, stoked, stuccoed, swatched, sweatsuit, sweetest, switched