This has only occurred once so far . Yesterday I was working outside in the yard for a couple hours. No breeze. At all. My son and I opened the side door to the house and it flew open with force and there appeared to be wind inside the house. It was so forceful that the door jerked from my hand and flew open. It wasn't a breeze. It was a like a big wind. I thought I had left a door or window open but I checked and no nothing was open. Got any explanations for me?