The photo was taken in early morning at Trout Lake, Yellowstone before any wind had come up. The temperature was about 20 F, so there were ice crystals forming along the side of the lake.
Note the bison at the far end of the lake - a few minutes after this picture was taken, he decided to occupy the only path down from this lake back to the valley, so we ended up having to bushwhack our way around him.

Randy Roig
Panasonic FZ-200