The Universe is a set of lyrics by Max Tyler. Trent doesn't think they make any sense, and doesn't think high schoolers will appreciate them (their next gig is at a high school party at Brittany's house). They are still arguing about the lyrics at the soundcheck to that gig.
Trent points out that all temperatures below zero are subzero, logically, the temperature can never drop below subzero. He could also have pointed out that there is no wind chill where there is no air, and that it doesn't make sense to compare "outer space" to "the universe", since "outer space" is "the universe" minus earth - and if earth is part of the universe it also does not make sense to say that it is a cold and black place. And since the universe is all of existence, it probably does not make that much sense to call it "a place".
The universe is a cold, cold place, black and bleak like outer space.
The wind chill drops below subzero, it's not no time to be a hero.