Charles E. Agnew, age 12, of Albany, New York, for his question:

What do they mean by a silver thaw?

This weathery expression is not as common as it used to be. It has quite a poetic ring. to it and perhaps we should try to keep it alive. A silver thaw happens in winter when the temperature is at or below the freezing point of water. The moisture outdoors is snow and ice. Sometimes we then get a shower of raindrops that happen to be at a critical temperature. The liquid moisture turns to ice the moment it touches a solid surface. Instead of being drenched with rainy water, the twigs and branches are coated in jackets of glassy ice. This weathery event may be called a silver thaw.

Something a lot like it may be caused by a few sudden changes in the wintery temperature. A warm spell may last long enough to melt the surface of the snow and ice. Then comes a sharp drop and the watery thaw freezes, adding a silvery sheen of glassy ice to everything outdoors. Some oldtimers stretch the meaning of silver thaw to include the frosty white rime that often comes with a chilly morning. But a true silver thaw is like silvery glass and it is caused by thin jackets of ice.