As the film crew of The Road prepared to shoot on one of the production's final days, the weather turned unexpectedly foul. It was early spring in Oregon, but the air was unseasonably bitter. The blue sky had been replaced by a blanket of gray haze. A light mist hung in the air. Miserable.

In other words, perfect.

While other productions pray for nice weather, the folks walking The Road -- a heavy, post-apocalyptic drama about a father and his young son struggling to stay alive as they trek to the coast -- were busy praying for hell. Overcast skies were a must. Cold rain was a bonus. Snow was worth slapping fives over.

"We needed it to look grim and do a lot of [the atmosphere] in camera, as opposed to a lot of other movies that rely on special effects for that kind of thing," says Viggo Mortensen, who plays the unnamed father character. "We had to count on the sky and everything looking right. We had mostly miserable, freezing, snowy weather, so we were lucky."

The film, opening Wednesday, is adapted from the Cormac McCarthy novel, and anyone who's read it knows what a dark, dangerous, inhospitable world the author created in those pages. Civilization has been destroyed by some unspecified cataclysm. Ash hangs in the air like snowflakes. Food is scarce. Buildings lie in ruin. Violent gangs patrol the highways looking for prey.

Creating the bleak, burned-out landscape described in the book was no easy task, but doing it correctly was vital.

"Everything looked and felt right," Mortensen says. "It was so harsh and so sad to look at, that it was like another character."

Much of The Road was shot in Pennsylvania, chosen, in part, for its wealth of dreary locales. (You won't be hearing that message from the state tourism board.) Director John Hillcoat filmed in old coal fields, a burned-down amusement park and, perhaps bleakest of all, Pittsburgh.

One of the film's crucial scenes, in which the Father and Son (played by Kodi Smit-McPhee) encounter a truck full of cannibals, was lensed on an eight-mile stretch of Pennsylvania highway abandoned in 1968 when a newer roadway bypassed it. Its pavement is now cracked and overgrown with weeds.

Sequences were also filmed in Hurricane Katrina-ravaged sections of New Orleans and near Mount St. Helens in Washington. In every location, Hillcoat took great pains to avoid any sign of a healthy world. Green grass was dressed with dust. Trees were stripped of buds. Filming halted when birds or planes appeared.

Mortensen says constantly inhabiting the post-apocalyptic world could be disorienting. The day after that cold day in Oregon, the weather cleared up, much to the chagrin of the crew.

"That day, I went to break for lunch, and I went out and thought, Wow, it's warm. So I sat down in the grass. I was stunned," Mortensen says. "I had been in this place and suddenly seeing this green grass and these things, they suddenly seemed extraordinary to me. The flowers and the cows and the clouds and the blue sky.

"I realized I had totally missed the coming of spring because I didn't want to know anything about it," he continues. "I'm someone who spends a lot of time outdoors, and that's not something I'd ever done before. It was sad."

The Road was shot last year, and was originally scheduled to hit theaters last fall, but its release has been pushed back multiple times, leading some to speculate the film was troubled. Mortensen disagrees.

"I didn't think they were going to be quite ready by autumn of last year," he says. "They were ready earlier this year, but they didn't want to put it out in spring. It didn't seem like that kind of movie to them. The fact that they waited a year isn't because it took a year more to do.

"I think they're probably right," he says. "It's that kind of story. There is something uplifting and spiritual about this story without being heavy-handed in any way. It seems appropriate as you're getting towards Thanksgiving and Christmas."

And, of course, towards awards season. The studio, The Weinstein Company, seems to be counting on bagging some Oscars, perhaps a Best Picture nod, now that the category has been expanded from five to 10 films.

To make the movie more audience-friendly, a voiceover was recently added. Mortensen's character provides narration that describes the world and clarifies his feelings, often by using language straight from the book.

"Could the movie have worked without it? Probably," Mortensen says. "But I think the reason they wanted to have it is because there's so much that's said in this book that's so memorable, as far as his description of things and so much emotion in the imagery. I think they wanted to have some of that to carry you along in the story."

The Road is still not an easy film to watch. Tears reportedly flowed at many of the festival screenings earlier this year. Whether the film's weighty vibe and bleak setting will put off audiences remains to be seen. Then again, with 2012 cleaning up at the box office, the apocalypse has never been hotter.