Jeff Fahey and his random scummy colleague have just a few seconds to get to their underground bunker before the Earth's temperature reaches... Absolute Zero! Yes, the temperature is going to be colder than space. But they can outrun it!
You have to love Absolute Zero, not least for the scene early on where Fahey's character explains the shitty, shitty science behind this "instant ice age" thing, and then looks at the camera and says, "Because science is never wrong." That's his catch-phrase, by the way. He repeats it at least a dozen more times in the movie, as the science gets worse and worse, delving into depths The Core never imagined.
As you can glimpse from the awesome graphic on the screen there, the extreme temperatures on Earth are caused by... wait for it... global tilting. And this is causing Antarctica to turn balmy, and even New York City becomes a tropical paradise. Yes, really. Miami is at absolute zero, but you can drive from there to a tropical paradise, as long as you can avoid the frosty winds and flying trees.
Here's what Wikipedia says about absolute zero, by the way:
Absolute zero is the theoretical temperature at which entropy would reach its minimum value. The laws of thermodynamics state that absolute zero cannot be reached because this would require a thermodynamic system to be fully removed from the rest of the universe. A system at absolute zero would still possess quantum mechanical zero-point energy. While molecular motion would not cease entirely at absolute zero, the system would not have enough energy for transference to other systems. It is therefore correct to say that molecular kinetic energy is minimal at absolute zero.
That certainly looks like what's happening in that clip, right? Sadly, it's still not as great as The Day After Tomorrow's "chased by cold" sequence.