All the cold and snow that winter brings to Wisconsin brings some super interesting weather phenomenon. Our oddly humid northern state is basically surrounded by water and that adds another layer to the strange and wonderful things that happen here in winter. You may have heard the words hoar frost before, but would you actually know what it is if you saw it? This super-interesting winter phenomenon may have a funny name, but it has a fascinating scientific background. Though the name sounds a little risque, it’s from the word meaning “gray, venerable, old” and the term hoar frost dates back to the late 1200s.

Most of us have gone outside early in the morning to find the world covered in frost, but have you ever taken a close look to see if it's a hoar frost?
Flickr/DanielHatton
What's the difference? When you see your back yard covered with these little frozen spikes, that's when you know we've experienced a hoar frost. It is, essentially, frost on steroids and it's really, really beautiful. Ground frost forms when the air is still and cold and water vapor in the air condenses on solid surfaces. When the temperature drops below freezing, ice crystals form and create frost.
Flickr/LaurenSobkoviak
The Oxford English Dictionary defines hoar frost as "expressing the resemblance of white feathers of frost to an old man's beard," which is a pretty amazing description.
Flickr/LaurenSobkoviak

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Hoar frost is essentially frozen dew. It happens when air is has a high dewpoint and comes in contact with something who's temperature is below zero. The water goes directly from its gaseous state to a solid state and form these little feathers or spikes, often on the edge of leaves. They can be susceptible to wind, so it's often possible to find hoar frost all "shooting" off an object.
Flickr/Geoff Sowery
When the water vapor in the air comes into contact with solid surfaces that are already below freezing point, ice crystals form immediately, and the ice continues to grow as more water vapor is frozen. Those are these funny little spikes that we see.
Flickr/Bob
Sometimes you'll find hoar frost in simple little locations around your yard, but it's also possible to see it spread over a whole scene as the tiny feathers of frost hop off every surface, making it all look a bit like they're all covered in a bit of a beard. It's a gorgeous, simple thing that happens in the winter that requires perfect conditions and a bit of science.
Flickr/Jean

Have you ever experienced this fascinating and beautiful weather phenomenon here in Wisconsin? With our humidity and moist air, it’s a lot more likely to happen than in other spots. Make sure you keep your eye out for it the next time you head outside on a cold morning.

If you’ve got hoar frost pictures, definitely share them with us either here or in our Wisconsin Nature Lovers Facebook group.

Have you ever heard of a frost quake? It’s another unique Wisconsin weather occurrence. Read all about it here.

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