There are hundreds of possibilities of what your "brown moths" could be, and with out photographs or actual specimens, I have no way to narrow down that list. I suspect you are seeing some kind of moth either in the family Noctuidae or the family Erebidae. These moths typically are referred to as 'cutworm moths', 'millers', 'armyworm moths and various other names. And there could be as many reasons as possible species as to where they came from and why they are there. Most of the caterpillars of these types of moths feed on weedy plants, crops, or grasses. So they could be coming from nearby crops, nearby fields, or even from you own lawns or gardens. They may be attracted by street and porch lights at night and just resting in the area during the day. Some might overwinter as the adult moths, and these could be moths seeking a place to hide out for the winter. Or they might be ready to lay eggs and eventually have their caterpillars or pupae overwinter. AS I noted above, I really can't be more specific without at least a close-up picture of one of the moths. If you could send me one, I will see if I can give you a more specific answer.