The ground is frozen and the water on the ground is part ice, part snow. Solid water, that is. But the air is slightly warmer and the precipitation is rain. Liquid water, that is. The temperature is hovering right around freezing, and the rate of precipitation is not enough to wash away the solid. It is not cold enough to freeze into (easily trampled) snow or ice, and not warm enough to dissolve the matrix holding the liquid in place.
What results is that the solid water is supporting the liquid water in a scaffold of slush. A sodden barricade which prevents all city drainage from working properly. The sidewalks are cold, sticky reservoirs supported on both sides by ridges from plowing and shoveling.
My winter boots are warm but not waterproof on the tops, so the slurry oozes in and collects around my foot. It is cold. My waterproof boots would fare no better, because although dry, they lack the insulation to protect me from walking through several inches of thick, icy goo. (I didn't get any photos, but the car tracks made a compelling case for snow tires, which parted the slush and gripped the ground, leaving a cleared trail behind.)
And through this, I commute.