Hi everyone, hopefully someone can shed some light on this odd smell that plagues my home during wet weather. I'm not DIY type person, so I may have missed something quite obvious. During wet weather, a sometimes faint, sometimes strong, sewer smell will enter my house. It's not always in the same spot, although it's always on my first floor. I was told it could be dry traps, so I poured water down all the drains, which didn't help. What's weird is this smell is not focused near any drain at all. I have a sump pump and the smell doesn't seem to be coming from that either. The smell will literally be smack in the middle of my living room. Tonight it was snowing/raining and the smell was in my dining room. I did notice that outside my house, specifically my back yard, had the same smell as my dining room, although this is not always the case. I should also mention that my town has a sewer system, so no septic tank. Any help would be appreciated.

Is there access to the attic ? I'd start by examining all of the vent work there.