Just about every year, we will thaw out during the winter. We lose the pretty snow cover, and what snow is left turns dirty and brown. It is clearly aesthetically displeasing, but it is quite beneficial for the plants in our landscapes.
We know that our plants need water throughout the growing season, but did you know that they need water during the winter also? It can be quite dry throughout the winter for the roots when the ground is frozen and all of the moisture is tied up as snow. But when the snow melts with a January thaw, that moisture becomes available and the plants will soak it up. This gives them a boost throughout the winter and prepares them for spring.
January thaws do not need to happen in January to be beneficial. The name does come from the idea that the thaw does happen typically in January. But, they can be good at any time during the winter.
During the winter of 2013-2014, a long, cold and snowy winter, we did not get a January thaw. Many plants were damaged from that because the winter was very harsh. There was not a chance for them to soak up any moisture. So any time we have a January thaw, despite it being ugly to look at, it is very good for our landscapes.