I was at the liquor store, “Eetz hot,” the man behind the counter proclaimed. It was hot, in fact. Last Monday afternoon had been sweltering, and it didn’t diminish the moist, chaffing ick of it to recall that the end of the week was forecasted to be ten degrees cooler.
“Yeah, it’s awful. I don’t even want to think about how hot it is in my apartment.”
Him, again: “Yesterday, I go home, and there are ninety degrees!”
Now, this actually stopped me. Even knowing he hadn’t yet mastered English idioms, I was not immediately sure what he meant. Then, I realized: It was ninety degrees inside his house when he got home. I’d just never heard anyone phrase it that way. I thought he was talking about, like, right angles — and godammit, homes need corners, as far as I’m concerned.
Then, the overthinking as I walked home: Isn’t it strange, grammatically, that the temperature is uncountable but nonetheless treated like a singular? Even when it’s almost always given a value of more than one? We say “It is ninety degrees” and not “They are ninety degrees.” If you had learned basic from-the-book English without understanding how it’s actually used, however, I think you might actually be inclined to say, “They are ninety degrees.” It makes logical sense — plural thing is plural thing, rather than singular thing is plural thing. That's how the guy in the liquor store put it together in his head, I'm betting.
Looking at the sentence “It is ninety degrees,” I’d say it looks like a predicate nominative construction — or what we use when we express the idea “X is equal to Y.” If I say “The boy is a murderer,” I’m saying that in this case, the boy is the same as a murderer — boy is the subject and murderer is essentially another subject, because you could flip the sentence around and it would basically mean the same thing. On either end of that is is a noun that being treated equally and assigned the same case. English-speakers would never say “The boy is murderers,” because that doesn’t make sense, yet that would seem to be what we’re doing with “The temperature is 90 degrees.”
Is it just that “The temperature is 90 degrees” is elliptical? We’re really expressing that “The temperature is valued at 90 degrees,” or something to that effect. But no one really says that either; we just say “It’s 90 degrees.” So at what point does a construction like this cease to be elliptical and just become standard grammar? If it’s not elliptical, how do you explain what’s going on here, grammatically speaking?