There are two forms of frost: rime and hoar. Rime frost occurs when the rate of frost formation is rapid, usually under conditions of high water content in the air (vapour and/or liquid) and at least moderate wind speeds. Rime formation is common during fogs where supercooled or near-freezing water droplets come in contact with subfreezing surfaces.
Rime frost has a grainy appearance, like sugar or salt, forming spikes, needles, or feathers and not having a recognizable crystal structure. Rime is opaque, less transparent than glaze ice formed during freezing rain episodes. Rime is denser and harder than hoar frost.
Hoar frost generally has a feather, fern, or flower pattern growing from the initial seed. Hoar frost forms only when winds are light, which is often the situation during clear, cold nights; thus it is the most common type of frost to those dwelling in non-mountainous areas. When we speak of frost, we are usually referring to hoar frost rather than rime frost.
Here is how it got its name ~~
Hoar-frost first turns up in written English in 1290 as hore frost. Strictly speaking, hoar-frost is the kind of frost that turns everything it forms upon white or gray. Due to the fact that hair turns gray with age, things that are white or gray are often associated with old age and this is the original sense of hoar. Old English har and Old High German her both meant "old" or, as a secondary meaning, "venerable, august".
Now remember I asked for a picture of it cuz I have never seen or so I thought I had not seen it before. Great pics greg thanks for sharing.
I'd never heard of hoar frost till just the other day when they brought it up, on ranchers. Course here in south east texas we dont get anything like that, but we do have a lil frost ever now and then.
I grew up in south dakota and seen frost many a times!!! But not once did i recall my family nor anyone else refering to it as "Hoar" frost. I know the type your refering to tho.....gets so heavy it downs powerlines and breaks tree limbs. Makes a pretty picture on a fence tho and the grass.....awww i miss it!