Why Mice Move Into Ontario Homes Every Fall (and How to Stop Them)
The first cold nights bring mice indoors across Toronto, the GTA and Barrie. Here is why it happens and the steps that actually keep them out.
By the Vermingo Pest Control team · October 29, 2026 · 4 min read
Every October, our phones fill up with the same call: “I think we have mice.” It is not a coincidence. As temperatures drop and fields are harvested around the GTA and Simcoe County, mice go looking for three things: warmth, food and shelter. Your home has all three.
How mice get in
A house mouse can squeeze through a gap about 6 mm wide, roughly the size of a pencil. The most common entry points we find are:
- Gaps around pipes, gas lines and A/C lines where they enter the house
- Worn garage door seals and missing door sweeps
- Dryer vents and roof vents without proper screens
- Cracks in the foundation and gaps under siding
- Openings where the roofline meets the soffit
Signs you already have mice
- Small dark droppings in cupboards, drawers or behind the stove
- Chewed food packaging, paper or insulation
- Scratching sounds in walls or ceilings, mostly at night
- A stale, ammonia-like smell in closed spaces
Why traps alone do not fix it
Traps catch the mice that are already inside. If the way in is still open, new mice keep arriving all winter. That is why so many people feel like they “had mice again” every single year.
Lasting control combines two things: removing the mice that are inside, and sealing the entry points with materials mice cannot chew through, like steel mesh, sealant and proper door sweeps.
What you can do this week
- Store food, pet food and bird seed in sealed containers
- Move firewood and clutter away from the house
- Check the bottom of your garage door for daylight
- Trim plants and shrubs touching the foundation
If you are already seeing droppings or hearing activity, it is time for a professional inspection. Our mice and rat control service finds every entry point inside and out, removes the mice and seals the gaps so you are not dealing with them again next fall.
Hearing scratching in the walls?
We remove mice and seal the gaps they use to get in.