昨日は激しく雨が降った。

yesterday

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

violent; furious; tempestuous; extreme; intense; fierce; fervent; vehement; incessant; relentless; precipitous; steep

rain

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

to descend; to go down; to come down; to be handed down (of an order, judgment, etc.); to pass (of time); to surrender; to capitulate; (often in neg. form) to be less than; to be inferior to; to have the runs; to have diarrhea