ERIE, Pa.  Cormac McCarthy’s Pulitzer Prize-winning novel, “The Road,” takes place in a world that, because of some unexplained catastrophe, has just about ended. The sky is gray, the rivers are black, and color is just a memory. The landscape is covered in ash, with soot falling perpetually from the air. The cities are blasted and abandoned. The roads are littered with corpses either charred or melted, their dreams, Mr. McCarthy writes, “ensepulchred within their crozzled hearts.”

For the crew that has just finished filming the movie version of “The Road”  a joint production of 2929 and Bob Weinstein’s Dimension Films, set to open in November  that meant an upending of the usual rules of making a movie on location. Bad weather was good and good weather bad. “A little fog, a little drizzle  those are the good days,” Mark Forker, the movie’s director of special effects, remarked one morning in late April while the crew was shooting some of the final scenes in the book on a stretch of scraggly duneland by the shore of Lake Erie here. “Today is a bad day,” he added, shaking his head and squinting.

The sky was blue, the sun so bright that crew members were smearing on sunscreen. A breeze was carrying away the fog pumping feebly from a smoke machine. Even worse, green grass was sprouting everywhere, and there were buds on the trees. Some of the crew had hand-stripped a little sapling of greenery, but the rest of the job would have to be done electronically by Mr. Forker, who was also in charge of sky replacement.

“The Road” began filming in late February, mostly in and around Pittsburgh, with a later stop in New Orleans and a postproduction visit planned to Mount St. Helens. The producers chose Pennsylvania, one of them, Nick Wechsler, explained, because it’s one of the many states that give tax breaks and rebates to film companies and, not incidentally, because it offered such a pleasing array of post-apocalyptic scenery: deserted coalfields, run-down parts of Pittsburgh, windswept dunes. Chris Kennedy, the production designer, even discovered a burned-down amusement park in Lake Conneaut and an eight-mile stretch of abandoned freeway, complete with tunnel, ideal for filming the scene where the father and son who are the story’s main characters are stalked by a cannibalistic gang traveling by truck.