Frost on autumn leaves
You can almost hear the sound of autumn leaves coated in frost as they crunch under your shoes on a walk through the woods. Though the calendar says it's still autumn, scenes like this highlight the colder temperatures as winter arrives in the Northern Hemisphere.
Radiation frost—the type seen in this lovely photo—is a quick transformation of water vapor to ice. When water vapor in the air comes into contact with surfaces that are at or below the freezing point, the vapor quickly crystalizes into frost. It can make for charming scenery, or a reminder that you should have worn a heavier jacket.