come [season] 够奇怪，come 可以用作介词

今天早上读到了这样一段话：The great Return to Office is grinding to a halt. Much of American Inc. had planned to get back to normal come fall, but Covid-19's delta variant had other ideas.

里面的惯用短语 grind to a halt 和 get back to normal 和 have other ideas 都很好理解，但是 come fall 显得很别扭，你是不是也这么觉得？在线语法检查器认为这个句子是正确的。后来我在 stackexchange 搜到了这个问答，并引到了这个更准确的问答。

你知道 come 可以作为介词 preposition 来用吗？我承认我不知道。它表示的意思是 at a particular time in the future or when a particular event happens。那两个问答里有几个此类用法的例子。

其实用英语句子分析器也有帮助。come 正好使用了第 26 条的用法，还附带了两个例子：

26. prep. Used to indicate an event, period, or change in state occurring after a present time.

1. Leave it to settle for about three months and, come Christmas time, you'll have a delicious concoction to offer your guests.
2. Come retirement, their Social Security may turn out to be a lot less than they counted on.