summer evening shower drenches one side of the street, leaving the other side dry.

Alternative form of 夕立は馬の背を分ける

even if one says

evening shower

かも知れません: (polite) Synonym of かも知れない (ka mo shirenai, “may, might, perhaps”)

かもしれない: perhaps

may; might / probably; maybe; perhaps

divide / sort out, separate / classify / share, let someone have / sell

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend