Frosty beauty: Where there’s rime, there’s a reason

By Nic Loyd, WSU meteorologist, and Linda Weiford, WSU News

SPOKANE, Wash. – After emerging from one of the coldest Januarys on record, including a so-called “Snowmageddon,” many of us have had it up to our ears with shoveling snow, slipping on icy sidewalks, driving through freezing fog and enduring frigid temperatures. Even our recent warmer weather and rainfalls can’t offset all the nippy days we’ve encountered.

Yes, it’s been a harsh winter in the Inland Northwest. But it has also been a beautiful one.

We’re talking about frost, a quiet phenomenon of winter when ice crystals form on objects such as tree branches, fences, cars and grass. Unlike snow, which forms in the clouds, frost is created near the ground when water vapor in the air encounters a solid surface that’s colder than the atmosphere surrounding it.

There are different types of frost and, this winter, we’ve been treated to some stunning visuals of them:

Hoarfrost on trees – a common site in January.

Hoarfrost. The most common, it’s what you’re most likely to find webbed onto your car windshield on mornings following cold, clear nights. Derived from the Old English word “hoary,” meaning white or gray with age, it’s the interlocking of ice crystals that often resembles salt around the rim of a margarita glass. Hoar frost coating tree branches makes for eye-catching morning scenes.

Rime often looks similar to hoarfrost but is formed differently and is thicker and more crusty.

Rime. Though it often resembles hoarfrost, it’s more dense and harder to scrape from vehicles. Not only do the two form differently, but they are created under different weather conditions. Whereas hoarfrost changes from water vapor to ice crystals, rime changes from water droplets to ice crystals. Freezing fog – which we’ve seen plenty of this season – produces just the right environment for rime to form. Water droplets suspended in air remain liquid until – BAM! – they hit a cold surface and instantly freeze.

Diamond dust is made of flat ice crystals on top of snow.

Diamond dust. You don’t have to see the animated movie, “Frozen,” to be enchanted by this frost type. Our own landscapes have displayed plenty of it. Also called snow sparkles, it occurs on sunny days when flat ice crystals top the surface of the snow. Light bounces off the ice crystals as if they were prisms, making them sparkle.

These phenomena, all created by ice crystals, demonstrate how winter’s hassles can be soothed by its frosty beauty.


Weathercatch is a bimonthly column that appears in The Spokesman Review. Nic Loyd is a meteorologist with Washington State University’s AgWeatherNet. Linda Weiford is a WSU news writer and weather geek. Contact: