A really cold day

It’s -13 F (or -25 C) at 8 a.m.  The screen door handle is so cold it sticks to what little moisture is on my fingers.  Both the upper and lower panes of my leaky kitchen window have a lovely crop of fern flowers.

The view looking out my kitchen window at the garage — cold!

Fern flowers are really quite pretty. For explanation of how they form, see my earlier post, Jan. 20, 2012.

Despite the chill, the chickadees, goldfinches, and nuthatches are already busy at the feeders.  You have to be impressed that such little birds that weigh less than or about the same as a packet of ketchup can stay warm in this frigid cold.

American Goldfinch, taken through my porch window. I’m not opening the windows today!

No bad weather seems to stop these little guys.

Fern frost

If you have leaky windows with semi-moist air on their interior and very low temperatures on their exterior, “fern flowers” or fern frost can form on the inside of the windows.

Such was the case this morning after a sub-zero overnight low:

The sun actually warmed up the thermometer a little; air temperature was -1 F.

And my kitchen window had grown a lovely crop of fern flowers overnight.

 

Easy to see why it’s called fern frost, since the ice crystal patterns resemble the leaves of a fern.  But why does it take this shape?

Moisture from the air condenses on the cold window, but instead of forming a liquid pool, the very cold window temperature causes the water to go directly from gaseous to solid state.  Ice crystals form around surface imperfections in the glass, like scratches, dust, or dirt (I’m sure there is plenty of that on these windows).  These initial ice crystals then serve as “organizing” points for the further deposition of ice, and eventually, a lacy pattern appears.

The cold morning air didn’t seem to bother the intrepid avian visitors to the feeders though.  They just fluffed up and toughed it out.

American Goldfinch enjoying a morning treat of thistle seed.

Black-capped Chickadees seem to be almost spherical in shape when fluffing out their feathers.