 Since the movie was actually shot in early spring in southern  California (as opposed to Illionis in late October), the crew had to  buy paper leaves from a decorator and paint them in the desired  autumn colors, then scatter them in the filming locations. To save  money, after a scene was filmed, the leaves were collected and  reused. However, as Jamie Lee Curtis (qv) and  John Carpenter (I) (qv) note on the DVD audio commentary, the  trees are quite full and green and even some palm trees can be seen,  despite that in Illionis in October, the leaves would probably be  mostly gone and there would be no palm trees.