It falls in the fall

LEAF

Think of what turns vibrant colors before drifting down from trees when the air grows crisp. It's not snow or rain, but something much lighter.

The clue plays on the double meaning of "fall." In autumn (also called "fall"), leaves drop from trees, so a "leaf" is something that literally falls during that season. The wordplay is simple but clever—it treats "fall" as both a season and an action to hint at the answer.