Yes, they celebrate Christmas in L.A. At least the random family in whose driveway Cameron confronts the police celebrates Christmas. In fact, we see giant inflatable decorations in their yard. Merry Christmas, buddy, he seems to be saying to Cameron. Here's a present: you won't get shot by the cops. No, no you don't have to thank me—it's from Santa.
Many people who celebrate Christmas, even those in L.A. dream of a white Christmas. Well, today is L.A.'s lucky day. In the first five minutes of the movie, a fellow cop says to Graham:
COP: I heard it might snow.
That would be quite the Christmas miracle, wouldn't it?
We don't hear much about snow for the rest of the movie. But at the very end, when we loop back around to the opening scene, it starts to snow. Snow, in L.A. It's a miracle. It's not quite as miraculous as all races getting along, but we have to take miracles where we can, no matter how small. And seeing L.A. covered in white is mira…
Hey, wait a minute. Did a movie about race really choose a fluffy white precipitation to be its closing image? Yes, yes it did. Make of that what you will.
We should also mention that snow in L.A. means that things are weird. Like, snow doesn't happen in L.A. It's as if things have got so bad on the ground that now the weather is getting all freaked out. Snow is also cold and impersonal—it keeps you at home, away from your neighbors—so it could also be showing us that all the lines of communication in L.A. have been broken beyond repair.