Actually, the snow isn’t melting, it is sublimating. Sublimation is the process of a solid (snow) going directly to the gas phase (water vapor). This is as opposed to solid (snow), to liquid (water) to gas (water vapor). What is needed for this to occur is energy (i.e. photons of sunlight), and/or the following: low relative humidities and winds. The thermodynamics of all of this are kind of complicated, but basically, nothing will happen to the snow without energy. So favorable conditions for sublimation would be having the sun close to over head (i.e. not low on the horizon), dry air, and a strong-ish wind. One other thing: I’m not sure if you mean that you are seeing water (i.e. melting) or if you are just observing snow piles/amounts decreasing over time. If you are seeing water, I don’t really know what is going on except for maybe if your city uses salt on the roads, this could be causing the melting. Salt lowers the freezing point of water, which aids in the melting of the snow, and keeps it from refreezing (but only down to certain temperatures. After all, there is a limit to all of our tinkering with nature.) Does this answer your question?