Like many other invaders, rats, mices, and voles head indoors when cold weather starts to hit. Our homes provide warmth, shelter, and food — an appealing arrangement compared to harsh winter conditions. Due to varying climates, it's difficult to pinpoint exactly when roden begins. However, you can typically expect it to start when the weather starts to cool, which can be as early as August or as late as October, depending on where you live in the U.S.