Chance Snowball’s Hell Don’t Loop Kay College Bad

1. Kay has a snowball’s chance in hell of getting into that college. She has bad grades and poor exam scores.
2. They don’t have a snowball’s chance in hell of raising enough money to send him on that trip, because they don’t have anything worth selling.

The expression suggests that the likelihood of something happening is as small as the probability that a snowball will not melt in the fires of hell.