Notes from a Naturalist: Behind the winter frost: It's all about dew point

As we move further into the cold season, a full two months past the autumnal equinox, it’s a good time to delve deeper into the wonders of frost. Frost is a distinct and ephemeral feature of our landscape, transforming it at sunrise and gone by the afternoon. At this time of year, there is a constant flux between frozen and unfrozen water. Unlike frozen water, which eventually covers the ponds and lakes and thickens throughout the winter, frost is at its best and most beautifully formed in this time between seasons, before snow covers the plants and their moisture-laden surfaces.

Dew and fog are two of my favorite ephemeral phenomena. But as the water temperatures cool off in November and December and surface waters match the air temperature, foggy mornings over waterways become a thing of the past. As the mornings drop below the freezing point of 32 degrees, dew will become frozen. Frozen dew is just that, though: liquid water from dew that freezes in the night, forming a smooth layer of ice over the ground and vegetation.