While walking back into my house from the back yard a waft of smoke blew in front of me. At first I thought it was from my neighbors chimney but I could not see any smoke. Next, I thought it was my son working in his workshop, maybe he was burning something out front. When I went to check, he wasn't there-empty workshop. So, I saw the smoke and smelled the smoke. I could find no explanation for it.
Any suggestions as to what it could have been?