Usage of “come”

Cole, I think this usage is related to the specific meaning of "come" as "happen." The word is used in much the same way in the following examples:

When what we want to happen finally does happen, we say our wish has "come true."

Also, in churning cream by hand, we say that the butter "comes" when the cream begins to separate and the specks of butter begin to appear in the buttermilk.

That is, "...you'll have them ready when the next [cooling] season comes [or happens]."

It's sort of a cop-out to just call the usage "idiomatic," but that seems to be the best that some dictionaries can do in this case.

Hmmm. Fascinating. It does sound awkward though, doesn't it?

It's colloquial. You can hear similar phrases by watching "New Yankee Workshop" on PBS, no joke.

Check out regional sayings in the U.S.

American Heritage Dictionary is great for etymology.

In the South, for instance, a common term is "I'm fixing to do something." Or if you're a native, it'd be pronounced "fixin' to"

"Fixin' to" is one of my favorite expressions. Billy Bard didn't say, but it means "getting ready to do" or "getting around to doing." For example:

"Honey, it's Saturday afternoon and you're just sitting there watching football. When are you going to change the oil in my car?"
"I'm fixin' to, just as soon as I finish my beer."

"I'm fixin' to go to McDonalds in a minute. Do you gals want a salad or anything?"

"I'm fixin' to take the kitten to the vet. Don't leave the house--your brother said he was fixin' to come over to help us hang the Christmas lights."