first frost of the year
Refers to the first frost of the autumn or winter season, often used in seasonal greetings or weather reports.
今朝、初霜が降りました。
We had the first frost of the year this morning.
初霜の知らせを聞いて、冬の準備を始めた。
Hearing news of the first frost, I started preparing for winter.
The first frost of the year fell on the garden this morning.
The first frost of the year was recorded in Hokkaido in mid-October.
It's now the time of year when news of the first frost starts to arrive.