。
I got caught in an evening shower and got drenched.
Literal
Evening-shower [with-に] encounter-[so-て], soaking-wet get-wet-[past-た].
夕立 ('sudden evening shower') is a seasonal word (summer), evoking a specific Japanese experience — the short, heavy downpour that breaks the humidity. 遭う (あう) here is 'to encounter [something negative or inconvenient]' — distinct from 会う, the neutral 'to meet.' びっしょり is a state mimetic (擬態語) for 'soaked through, drenched,' often paired with 濡れる. The pair び っしょり濡れる is so stable it almost counts as a collocation.