set in

US /set ɪn/
UK /set ɪn/
"set in" picture
1.

始まる, 定着する

When something unpleasant or difficult sets in, it begins and seems likely to continue.

:
The rain set in for the entire weekend.
週末中ずっと雨が降り続いた
Once the cold weather sets in, it's hard to get rid of it.
寒い天気が始まると、それを取り除くのは難しい。
2.

定着する, 募る

If a belief or habit sets in, it becomes fixed and difficult to change.

:
Once bad habits set in, they are hard to break.
悪い習慣が定着すると、なかなかやめられない。
A feeling of despair set in after the news.
そのニュースの後、絶望感が募った