The temperature is minus 13 degrees and falling, as January's cold sun sinks below the horizon. Let's layer on the thermax and down, pull on the Sorels, button up the storm-flaps on our parkas, and leave the warmth of the Visitor Center for a twilight geyser walk. Walking is hazardous, so grab a ski pole for stability. The snow, packed 2 feet deep on the boardwalk, disappears abruptly at each runoff channel.
Warm water prevents snow accumulation but adds plenty of moisture to freeze into a glaze of ice.
Watch out, too, for the deep holes left each time a bison steps on the path. As we circle around the geyser, the only sound is the squeaky crunch of subzero snow underfoot. Benches that in summer are packed with tourists now lie buried in deep snow. Ahead is a bare, steaming patch of ground that has been collapsing and growing warmer every year. Bison standing like huge, frosty boulders are drawn here each evening seeking comfort from the frigid night air.