Get us some pictures next time.
Man, I thought about it, but didn’t get around to it, not sure what hosting site I have, etc. But as evidence I was not imagining it, my sister came over this morning for a bike ride and entirely unprompted said, “Why are you the only ones w/ snow there?” And as we biked, we could see many places where the only frost/accumulation was at the driveway/sidewalk intersection.
I have lived mostly in the southern US and we had a deep freeze in Houston in 2021 where we had snow for the first time. We live in the suburbs and in a planned subdivision and saw the same phenomenon as the OP describes.
In our case, the sidewalks have large concrete storm drains under them. The concrete drains act as heat reservoirs pumping up ground heat. Streets have thicker concrete with the same effect. Here are some pictures taken from the internet to show that many subdivision sidewalks are sitting on storm drains :
