It was a particularly cold day when it came time to film the carnival scene and was physically exhausting for the actors. Even though it was filmed in the south near Birmingham, Alabama, it was freezing. It was shot through the night into the next morning. Temperature was 32 degrees with 10 mph wind gusts.
The name of the town in which Ana and Freddy grew up is Pearl. Wild-cultured pearls are best known from being discovered in oysters and other mollusks, but the allegorical use here is that it is a precious center of a town that is apparently going to be destroyed by the Black Fog (which has, of course, another meaning, not to be spoiled here). Just as a pearl is surrounded by the mollusk that produced it, and just as the mollusk is surrounded by the sea, the town of Pearl is surrounded by what appears, at first, to be a home-like quality, which is soon surrounded by a greater darkness.
Film debut of Madison Lintz.
Ashley Nicole Blevins (one of the carnival scene extras) was dubbed "The Sledgehammer Girl" by one of the directors. Ten years old at the time, they had her playing the game where you swing the sledgehammer to test your strength and try to ring the bell.