On cold winter days, we usually don’t think on ice or frost except when we have to scrape it off the windshield of our vehicles, or salt the walkway so we don’t slip and fall. Occasionally, especially when it is very humid or foggy and below freezing, or we are right next to a stream or river, we can see a more interesting frost. You may notice that vegetation and other objects are covered with a fuzzy coating of white; a closer inspection reveals that this “fuzz” is actually many ice crystals in the form of needles. This is hoarfrost.
Hoarfrost forms when the air is saturated with humidity and the temperature is below freezing. This usually entails fog but can also be seen near stream banks where the humidity is high without the fog. Interesting branches may be seen coming off the straight needle like crystals. Water molecules, randomly bouncing around in a drop of dew at room temperature, form an orderly crystal structure when the temperature hits the freezing point.
Very cold mornings along the river valley are the best time and place to witness this phenomenon, but you can also find smaller examples right along creek banks and other areas where open water flows. Marylin Lott, in her poem “Hoarfrost Magic,” sums up the impression one can get witnessing white landscapes of hoarfrost; in her last verse she writes:
So if you are so fortunate
To see the hoarfrost magic
Grab your camera and capture
Nature’s icy antics!