Chris, I saw the little cottony things floating in the air and like you, I realized they weren't exactly floating, but were actually flying. It is some type of aphid in the family of "Wooly Aphids." When you see them in the summer they are moving from their Primary Host to their Secondary Host. They require two types of trees to complete their lifecycle. For instance, the Wooly Alder Aphids starts out on a Maple tree, then in May or June they leave the maple, and must find an Alder tree to complete their lifecycle. Primary host, secondary host, etc. It was very interesting reading about these little fluffs.
The bad news is that a heavy infestation of any kind of aphid can damage a tree by continually, year after year, sucking the sap from it. Also, if there is a heavy infestation aphids can leave "honeydew" or a sticky film on things under the badly infested tree. It can be an icky mess.
Yours are really cool, Tigger!
Start slowly . . . then taper off.