Lake Mendota froze officially on January 34, www.fishing.info/engberg_12_08_11.html2021. The median freeze date date for the lake is December 20th. With the lake freeze, the tundra swans and other water fowl left, and a new set of lake water foragers has arrived: Ice fishermen. Their arrival completes the annual cycles until spring sets in.

The deeper waters off Picnic Point are a hot spot for good sized perch. At this time, walleyes are still found in water less than 15 feet deep, but as the winter progresses, they will move to mid-lake. Also this early in the year, the fishermen catch fish attracted to the various baits throughout the day, but as winter progresses the best times are early morning and the later in the day. (see http://www.fishing.info/engberg_12_08_11 for more information on good ice fishing spots in Lake Mendota) 

​​Rime frost and its cousin hoar frost have dazzled observers with their beauty since ancient times. In his book Μετεωρολογικά, Meteorologia, Aristotle noted
"Both dew and hoar-frost are found when the sky is clear and there is no wind. For the vapour could not be raised unless the sky were clear, and if a wind were blowing it could not condense." (347a26-28)
 
The term hoar frost derives from hoary which means gray or white in medieval English of the 14th century, and was used as adjective for a person with a white beard and hair. Hoar frost forms when water vapor in moist air comes in contact with objects that are well below freezing, like trees and grass during freezing night in winter, often with starry skies above. Here the water vapor, a gas, changes its state directly into a solid, the ice on the trees and surface objects, and we have frost.
 
The term rime frost derives from the 12th century, old Norse term hrīm or rimfrost. Conditions for rime frost are less likely in Greece or in England than for hoar frost, but occur regularly in snow covered northern landscapes like ours. Rime frost can form when layers of fog or mist develop in moist air over snowfields during cold nights with temperatures below freezing. The fog consists of tiny water droplets, cooled below freezing and suspended in the cold air.

Being both a meteorologist and historian of science by training, I take pleasure in tracing how people have always been fascinated with special weather phenomena and have tried to describe and explain them. We are grateful to Steve Sentoff for providing the photos. 

After Madison’s Lake freeze, the tundra swans on University Bay will continue their migration to open waters in the Chesapeake Bay and elsewhere. During the migration period they gather in huge flocks. It is believed that the tundra swans mate for life. But after they mate and have reached their breeding grounds in the northern tundra, they fiercely defend their large territories and live as solitary pairs. ​