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Too cold....
The solstice deals with the position of the sun at sunrise and sunset but has little effect on its up and down motion. It does relate to the actual times of sunrise and sunset. I think that the picture simply indicates that the sun melted the non-shadowed frost on the road after it rose, and the photographer just happened to catch it. Solstice day was not a factor other than winter is the time when frost can be on the road.