Factual error: Near the end of the movie, Jamie Lee is speeding down a road in the coroner's van she has stolen and Michael is attacking her from the back of the van. She slams on the brakes, and he flies into the front windshield, which shatters into many pieces. Windshields are made of laminated glass, which contains a sheet of plastic, sandwiched between to sheets of glass. It does not shatter when struck.
Continuity mistake: In the beginning Laurie is in the shack hiding from Michael Myers when Buddy comes in and sets down the donuts and coffee he had on the desk, he hands her the coffee and goes to get his car. When Michael is looking through the window, you can see the whole desk and the donuts are gone.
Factual error: Some of the scenes show trees without leaves which is correct, but several of the scenes have Myers walking through fields of crops (probably beans) in Illinois, and the trees look full, neither which could be true in late October, as the crops would be harvested or wilted by then, and the trees bare.