Well, Jack Frost looked up and realized that the clouds hid the sun. There could never be a shadow that day. At least not a real shadow.
15 seconds sound clip from the Jack Frost (1979) movie soundboard.
You can hear this line at 00:38:48 in the Blu-ray version of the movie.
Quote context
[...]
- When she gives me a certain sign, I know it's my time to leave.
- At this very moment, he is starting to awaken. Very soon, he will leave his home.
- If he stays outside, and is not frightened by his shadow, that will be my sign to move on.
- But if his shadow frightens him?
- Of course, that didn't eliminate magic shadows.
- It's an easy occupation. I'm only workin' once a year.
[...]