A number of years ago the city replaced the Norway maples that had lined the street with an assortment of trees that in this block are over represented by Callery pears. (The Norways were killed when they city dug up the street in a sewer/run-off separation project.) The "snow" was petals from the flowers on the trees.
The wind has calmed down and so has the running about. The exhausted cat is currently asleep on a pile of toys.