When temperatures drop in fall and winter, mice might seek your home for food and shelter. And it only takes a quarter-inch gap — about the diameter of a pencil — or a hole as small as a dime for them to squeeze through and make it inside.

Here’s your guide on how to protect your home from any uninvited mouse friends.

Where they get in

There are many small, hidden places mice can use to get inside your home. Here are some spots to check for gaps:

• Cracks in your foundation
• Gaps around windows and doors
• Openings near utility lines — gas, sewer and water
• Indoor pipes — including around a washing machine, sinks, furnace, AC unit, and water heater
• Dryer vents and exhaust fans
• Vinyl-siding corners
• Garage doors
• Holes in the corners of closets, kitchen cabinets and pantries
• Fireplaces and chimneys
• Attics, basements and crawl spaces
• The space where gutters connect to the fascia board
• The roof — check eaves, soffits, gables, rafters and vents

(MORE: Fall homeowner checklist: Do these 17 things before winter)

You can also check for signs of mice to see if you already have an infestation: droppings that resemble tiny brown pellets, sounds of chewing and scratching, smells like urine, chew marks on food packaging and nests.

Preventative measures and how to seal gaps

If you’re not a DIY-er, the first and easiest thing you can do is call a pest control expert or rodent exterminator to inspect your home and seal gaps for you. This will typically run from $200-$600, with the average cost at about $400. 

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The advantages of doing this are saving time and ensuring you don’t miss any spots you wouldn’t think to check.

If you do want to do it yourself, first make sure the materials you use to seal gaps are chew-proof — no plastic or wood.

Here are some supplies you might need and their estimated costs:

• Steel wool: $5–$10 per package
• Steel mesh: $20–$40
• Caulk and supplies: $10–$30
• Expanding foam: $5–$10

Caulk is good for sealing cracks around walls and doors. Steel mesh is great for covering areas like a dryer vent or chimney.

You can stuff any mouse holes you find with steel wool and seal over them with caulk.

You can also add bricks to your home’s siding or foundation if needed. Keep areas like your roof and fascia maintained, as storm damage or rotted boards can create mouse problems.

(MORE: Why your house creaks in fall and winter — It's not haunted!)

Mice also really dislike the smell of peppermint, so a cotton ball soaked in essential oils left in a place you might see them is a good deterrent.

Keeping your home clean, avoiding leaving out food or dirty dishes, and regularly taking out the trash far away from the house are good preventative measures.

Maintaining yard work, trimming tree branches that act like bridges from the ground to your rooftop, and keeping wood piles far from the house help as well.

The dangers of mice — including house fires

Mice can bring health dangers, carrying diseases and contaminating your food, countertops and dishes with their feces. 

This can happen by even just breathing in air contaminated by rodents. Or you might even get bitten by one. They also carry ticks, mites, or fleas that can spread diseases.

And they can chew through and damage much more than you’d want them to touch: food boxes, baseboards and gas lines, just to name a few.

But one somewhat unexpected and extremely worrisome outcome is the possibility of a house fire.

(MORE: The $150 you skip now becomes a $500 emergency by the first cold week of the season)

Fire investigators estimate 20–25% of "unknown cause" fires are due to rodents, often from chewing wiring. In this case, you could lose your entire home, everything in it or even loved ones or pets.

They also multiply easily, so if you don’t stop the problem early, you can end up with entire families of mice nesting in your home.

So, as cold weather approaches, now is the time to seal holes and get ahead of the issue before you find signs of mice in your home.

Content writer Ada Wood enjoys exploring the stories that science and climate teach us about our natural world and how it influences the way we live in it.