Left the Old Faithful area where the temperature was 8°F and arrived at Norris at sunrise. Was probably even colder there. Turns out it is possible to sit and wait for a geyser at such temperatures, if you have a couple of blankets and are wearing lots of layers. The day never really got above freezing, although some places in sunlight did dry out a bit.
New Crater had some good surges early in our wait, then nothing much happened until a hour before we planned to leave. Even this activity wasn't encouraging, as I only got the phone out just in case, but never started recording. So it was mostly 9 hours of killing time.
Years ago I came across an interesting phenomena of hot ground, and encountered it again today. When warm, damp ground encounters frigid air, frost develops underneath pebbles and particles lying on that ground. That ice in turn causes the frost to grow, from the bottom, slowly pushing the top of the frost column up. I found large patches of this frost over by Echinus, on both sides of the boardwalk.