。
There was a frost last night.
Literal
Last-night frost [subject-が] fall-[past-た].
霜が降りる ('frost falls') is a fixed Japanese collocation — in English we'd say 'there was frost,' but Japanese imagines frost as falling like snow or dew. 降りる (ori-ru) here is 'to come down' in a general sense, distinct from the common 'to get off' for vehicles. A quietly poetic image of winter.