Unidentified Pest

The backfence neighbor isnt very good about upkeep--the whole yard behind us is weeds, weeds and more weeds, a gallery of them. Although this feathery thing is quite beautiful on its own, there are a gazillion of them floating around on our side of the fence right now, lodging in all the trees and bushes. It isn't a dandelion, that's all I know. 
Another day of not going out, except to take this photo. Bad air, even though the sun was out for a few minutes.