It’s sparkling clear and the ambient temperature is 12 degrees (F) here, as I write. There is little wind, so there is no significant windchill to make noses even colder. Recent rains have cleared away virtually all of the snow; the ground is frozen hard; moss is crunchy underfoot, and spring-fed streams are running through ice tunnels of their own making, as you see in this image from yesterday.
I’ve always wondered how those streams make their own ice tunnels, since water freezes at 32 degrees whether or not it’s flowing. A little research indicates that the first event in building a stream ice tunnel is surrounding air that is much colder than 32 degrees.
That’s because flowing stream surface water mixes with water below that is higher in temperature and has trouble getting to 32 and staying there. However, when it gets cold enough long enough, the churning of the water can’t stop surface waters from staying at 32 or below and turning into ice. This surface ice can protect the water below and keep it flowing at above 32 degrees.
If, however, it gets very, very cold over time, the temperature of the entire flowing stream can be driven to below 32 degrees long enough to freeze the whole stream into a sculpture of itself. (Image taken in Brooklin, Maine, on January 18, 2022.)