Filming in the mountains near Big Bear, California was made more difficult when the cast and crew were slowed by a cold and soggy storm that lasted four days. The local media labeled it "the worst rain storm to hit Big Bear in one hundred years." Despite the foul weather, the cast and crew continued filming.
After initially filming a version that would likely earn a PG rating, the director later shot more graphic monster attack footage that would better the chances of an R rating.
When the bad weather hit, local vendors in Big Bear donated rain gear and dozens of pairs of dry socks to the crew.