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Hoar frost swaths every weed and tree at Sawhill Lakes in diamonds.
Hoar frost swaths every weed and tree at Sawhill Lakes in diamonds.

When conditions are right, hoar frost sugarcoats each twig and each spindly weed as the sun rises.

Several times this month conditions have been perfect to revel in the magic of inch-long frost feathers. A bonus is that most people prefer a hot cup of coffee to a frigid foray outdoors so you may have the trail to yourself.

A robin, looking perky in spite of the cold, sits on a hoar-frosted picnic table on the shore of Coot Lake.

Hoar frost phenomena are especially dramatic along streams after a cold, clear, night when moisture transmutes from vapor to solid, skipping the liquid phase. Rime frost, a similar creation, occurs when fog freezes on contact. These needle-like spikes lack the crystalline detail found in hoar frost. Since we have trouble distinguishing rime from hoar, we usually refer to both as “hoar frost.”

As the sun climbs, delicate frost formations disappear, but sunlight may then splinter tiny, airborne ice crystals into jewels we call “fairy dust.” Ice crystals — acting as prisms — also create iridescent effects in clouds. Haloes, sundogs, and sheets of opalescent color occur when ice crystals in cirrus clouds near the sun refract light.

Moon haloes — concentric bands of luminous gold, red, and turquoise — glow mysteriously on cold nights. Crystals that are numerous and uniform in size create the most intense colors.

During thaws, listen for the break-up of ice on frozen lakes — the crystalline music signaling the end of winter.

Here are five favorite frosty footpaths

  • East Boulder Trail, White Rocks segment. Starting at the northwest end of the parking lot the trail drops, crosses Valmont, and follows Dry Creek north passing east of a large lake and wetlands often filled with birds. Just before sunrise, alpenglow sometimes makes the Indian Peaks blush pink. We usually turn back when we reach the bridge over Boulder Creek, but you can continue on to Gunbarrel Hill skirting the White Rocks State Natural Area (closed to the public) if you like. Go east on Valmont and turn south into the parking lot about a mile beyond 75th.
  • Sawhill and Walden Ponds. This complex of lakes, ponds, and wetlands sometimes transforms into a frosty fairyland where you can wander on a myriad of old roads and trails formerly used by gravel mining trucks. Now more deer inhabit the area than in 1900 when George Sawhill never saw a single one. It’s also one of our favorite birdwatching spots where we recently spotted eastern bluebirds. From the intersection of Valmont and 75th turn north. In a short distance, turn west at either of the signs.
  • Coot Lake. A path circles the lake featuring nature paintings and quotations. Nowadays Wendell Berry’s quote seems especially apt: “When despair for the world grows in me … I come into the peace of wild things who do not tax their lives with forethought of grief. I come into the presence of still water … ” This loop trail connects to a trail heading west to Boulder Reservoir where bald eagles sometimes sit on the ice. From the Diagonal Highway, turn west on CR 39. Coot Lake is on your left in. 0.7 miles
  • Boulder Creek and Skunk Creek Confluence. Boulder Creek Path between Scott Carpenter Park and Arapahoe Avenue is less congested than stretches farther west and in spring is a hot spot for migrating birds. Now, it’s a cold spot for frost sculptures. A dragonfly engraved boulder marks the confluence of Boulder and Skunk Creeks. Walk up Skunk Creek Path to College Avenue and check out the wetlands on either side for muskrats, wood ducks, and other surprises. Park at Scott Carpenter Park, 30th and Arapahoe. Walk to the creek and head east.
  • Walter Orr Roberts Trail. Sometimes frost works its magic on up into the foothills, flocking each needle of ponderosa pines and junipers. This short nature trail goes west from the National Center for Atmospheric Research and is ideal for enjoying atmospheric astonishments while reading about them. As though the frost were not miracle enough, several mule deer bucks sparred in the field below NCAR just before Valentine’s Day as though preparing for romance. Take Table Mesa Drive west to the NCAR parking lot.

Ruth Carol and Glenn Cushman are the authors of “Boulder Hiking Trails” published by West Margin Press.