The short answer: mice come inside in the Inland Northwest from about October through February, when nights drop below freezing. They get in through gaps as small as a quarter inch, usually around garage doors, utility lines, dryer vents and foundation vents. The fix that lasts is exclusion: find and seal those gaps, then trap or bait the mice already inside.

Why mice move in when it gets cold

Field mice and house mice spend summer outside in fields, wood piles and landscaping. When temperatures in Post Falls, Rathdrum and the Spokane Valley start dipping below freezing, they look for warmth and food. Homes on the edge of open ground, new subdivisions and anything near the Rathdrum Prairie fields tend to see them first.

Signs you already have mice

• Droppings the size of a grain of rice in drawers, under sinks or along garage walls
• Scratching in walls or ceilings at night
• Chewed food packaging, insulation or wiring
• Nests of shredded paper or fabric in storage boxes
• A musty, ammonia-like smell in closed spaces

Where mice get in

On a typical Crosstown rodent inspection we find entry points in the same handful of places:

1. Garage door corners, where the weather seal is worn or doesn't meet the slab.
2. Utility penetrations, where gas, water, AC lines or cable enter the house.
3. Foundation and crawl space vents with damaged or missing screens.
4. Dryer and bathroom vents without a flap or cover.
5. Gaps under siding and where the siding meets the foundation.

DIY steps that help

• Replace worn garage door seals and add a door sweep.
• Stuff small gaps with copper mesh, then seal with exterior caulk or foam. Foam alone gets chewed through.
• Store pet food, bird seed and grass seed in sealed bins.
• Move firewood at least 20 feet from the house.
• Set snap traps along walls, baited with peanut butter, and check them daily.

When to call a pro

If you are still catching mice after a week, hear them in walls, or find droppings in more than one room, there is usually an entry point you haven't found. Our rodent service includes a full inspection, exterior bait stations, interior traps and weekly follow-ups for 3 to 4 weeks while we seal entry points. The initial rodent service is $349 with a recurring plan, or $699 without one. See details on our mouse and rodent control page.

Common questions

How small a hole can a mouse fit through?

About a quarter inch, roughly the width of a pencil. If you can fit a pencil in a gap, a young mouse can get in.

Do mice leave on their own in spring?

Rarely. Once mice find food and warmth inside, they nest and breed. A single pair can become dozens in a few months.

Are mouse baits safe around pets?

We place bait inside locked, tamper-resistant stations outside the home, and use traps inside, so pets and kids can't reach the bait.

Do you handle mice in Coeur d'Alene, Hayden and Spokane?

Yes. We service Post Falls, Coeur d'Alene, Hayden, Rathdrum, Spokane, Spokane Valley and Liberty Lake.

Need help now? Call or text Crosstown Pest at 208-401-6122 (Mon to Fri, 8 AM to 6 PM). Most homes start at $41 a month, and every plan includes our 365 Pest Free Guarantee.