After making the snowmen in the next scene the grass is green. Later that evening the snow is back.
The snowmen all look fake. You can see the cotton fibers on them and they move when touched.
The movie takes place just before Christmas, and it was shot in the winter as there are bare deciduous trees everywhere. However, there is a small difference between mid December and late February / early March - you can hear loud singing by singing birds in the outdoor scenes, and they don't sing between early autumn and late February or early March.
About 1 hour 10 minutes into the movie at the center, the boom mic is seen moving as reflected by the glass to the next room.