Why Mice Move In When Tennessee Turns Cold, and How to Keep Them Out

The first chilly nights of fall are when many Middle Tennessee homeowners hear it: a faint scratching in the walls or the attic after the house goes quiet. More often than not, it means there are mice in the house, and they’ve decided your home is the warmest, best-stocked place on the block to spend the winter.

Why mice move in when it gets cold

House mice don’t hibernate. When temperatures drop in the fall, they look for a way into homes, traveling along the outside walls, drawn by warmth and the smell of food (University of Arizona). A house offers everything a mouse needs to get through winter: shelter, nesting material, and a steady supply of crumbs, pet food, and pantry goods.

Mice are also looking for water and food sources in dry weather, so a long dry spell like the record-dry September we just had doesn’t make them any less interested in your home.

How they get in

Mice need much less room than most people think. An adult house mouse can squeeze through a gap the size of a dime, and young mice can get through an opening the width of a pencil (University of Arizona). That means the small gaps most of us never notice are open doors to a mouse.

Common entry points on Middle Tennessee homes include:

• Gaps under garage doors and worn door sweeps
• Spaces around pipes, wires, and cables where they enter the house
• Dryer vents, attic vents, and crawl space vents without screens
• Cracks in the foundation and gaps where siding meets the foundation
• Openings around plumbing under kitchen and bathroom sinks

Mice can also hitch a ride inside in storage boxes, especially ones kept in a garage or shed (University of Arizona).

Signs of mice in the house

House mice are nocturnal, so you’re more likely to see what they leave behind than the mice themselves (University of Arizona). Watch for:

• Droppings. Mouse droppings are about 1/8 to 1/4 inch long, similar in size and shape to grains of rice (University of Arizona). You’ll usually find them along walls, in cabinets and drawers, and behind appliances.
• Gnaw marks. Any small hole with chewed edges is a sure sign (University of Arizona). Check food packaging, baseboards, and the corners of cabinets.
• Rub marks. Greasy smudge marks along walls, pipes, and beams show where mice travel. Clean them up, since they carry chemical cues mice use to communicate (University of Arizona).
• Sounds at night. Scratching or scurrying in walls, ceilings, or the attic after dark.
• Shredded nesting material. Bits of paper, insulation, or fabric tucked into hidden corners.

Why a few mice are worth taking seriously

House mice breed rapidly (University of Arizona), so a couple of mice in October can become a much bigger problem by spring. Along the way, they urinate continuously as they travel and leave droppings frequently, contaminating food, counters, and other surfaces (University of Arizona). They also chew on electrical wires and wooden beams, damaging homes and furniture (University of Arizona).

Mice and rats can also trigger asthma and make it worse (U.S. Environmental Protection Agency), which matters for families with kids or anyone with breathing problems. House mice, the kind most often found indoors, haven’t been found to carry hantavirus (University of Arizona), but their droppings and urine still need to be cleaned up carefully.

How to clean up after mice safely

If you find droppings, resist the urge to grab the vacuum or a broom. The CDC says not to vacuum or sweep rodent urine, droppings, or nesting materials (CDC), because it can stir contaminated particles into the air. Instead, follow the CDC’s approach:

1. Put on rubber, latex, or vinyl gloves.
2. Spray droppings and urine with a bleach solution or an EPA-registered disinfectant until they’re very wet (CDC), and let it soak for a few minutes.
3. Wipe everything up with paper towels and throw them away in a sealed bag.
4. Clean the surrounding countertops, cabinets, drawers, and floors with disinfectant (CDC).
5. Wash your hands well when you’re done, even after wearing gloves.

The CDC also notes that fleas are common on rodents, so consider insect repellent on your clothes, shoes, and hands when picking up dead mice or nests (CDC).

How to keep mice out this winter

• Seal the gaps. Close openings of 1/4 inch or more with a flexible sealant that stretches as the house expands and contracts, and use hardware cloth for larger openings like vents (University of Arizona).
• Check doors. Replace worn door sweeps and weatherstripping, especially on the door between the garage and the house.
• Store food in hard containers. Adult mice can chew through zip-top bags (University of Arizona). Use glass, metal, or hard plastic containers for pantry goods and pet food.
• Clear the clutter. Keep firewood, boxes, and stored items off the ground and away from the house, and declutter garages, attics, and basements where mice like to nest.
• Act on the first sign. One mouse is rarely just one. The sooner you deal with it, the smaller the problem stays.

How U.S. Pest helps

Our rodent control service starts with a free inspection. Your technician will look for signs of activity inside and out, find where mice are getting in, and recommend a plan to remove them and keep them out. Not sure whether you’re dealing with mice or rats? Our Tennessee rodent identification guide can help.

Hearing scratching in the walls? Call 615-590-1260 or schedule a free inspection. Everything we do is backed by our Whatever It Takes Guarantee.

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