When temperatures drop across Wisconsin, many homeowners assume pests disappear until spring. Unfortunately, mice don’t follow that rule. In fact, winter is one of the most active seasons for indoor mouse activity—especially in areas like Milwaukee and surrounding communities.

As outdoor food sources disappear and cold weather sets in, mice shift their focus indoors. Homes offer exactly what they need to survive winter: warmth, shelter, and reliable access to food. Once inside, mice can remain active all winter long, quietly nesting inside walls, basements, attics, and crawl spaces.

One of the biggest reasons winter mouse problems go unnoticed is that activity often happens out of sight. Mice typically travel behind walls, under appliances, and along utility lines. Homeowners may not realize there’s an issue until they hear scratching sounds, notice droppings, or discover chewed food packaging.

Wisconsin homes are particularly vulnerable during winter because of how buildings expand and contract during freeze–thaw cycles. Small gaps can open up around foundations, siding, vents, and utility entry points—creating easy access for mice. Even an opening the size of a dime is enough for a mouse to squeeze through.

Another factor is reproduction. Mice do not hibernate, and indoor conditions allow them to breed year-round. A small winter problem can quietly grow into a much larger issue by spring if left unaddressed.

The best way to manage winter mouse activity is through prevention and early intervention. Sealing entry points, reducing clutter, storing food properly, and addressing moisture issues all help reduce attraction. Professional pest control adds another layer of protection by identifying hidden entry points and nesting areas that are easy to miss.

If you’re noticing signs of mice during winter, it’s not something to ignore. Addressing the issue now helps protect your home, prevent damage, and reduce the likelihood of ongoing problems when warmer weather returns.

Winter may feel quiet outside—but indoors, mice are very much awake.