Every year, calls about mice climb sharply in the first two weeks of October. It isn't coincidence and it isn't bad luck — it's a temperature response you can plan around.
The trigger is a sustained drop, not a cold night
House mice start seeking shelter when overnight lows stay below roughly 50°F for several days in a row. Across New York City and Long Island, that usually lands in the first half of October. A single cold night does nothing. Four or five in a row moves an entire outdoor population toward the nearest structure with heat, food and quiet.
They need less space than you think
An adult house mouse fits through a gap the width of a pencil — about a quarter inch. That means most homes have a dozen or more viable entry points that no one has ever noticed:
- The gap where a gas or water line enters the foundation
- Garage door corners where the rubber seal has hardened and pulled back
- Dryer vents with a broken or missing damper
- Sill plate gaps behind old siding
- Basement window frames that have settled away from the masonry
In Brooklyn and Queens row houses, add shared party walls and cellar hatches. In Nassau and Suffolk, add crawl-space vents and attached garages.
Why bait alone fails
Bait reduces the population that's already inside. It does nothing about the opening that let them in, which means next October you're making the same phone call. Any rodent program that doesn't include physical exclusion is a subscription, not a solution.
Proper exclusion uses materials mice can't chew: copper or stainless mesh packed into gaps, mortar over masonry openings, metal flashing on chewed wood edges, and new door sweeps. Steel wool rusts and expanding foam gets chewed straight through — neither belongs in permanent work.
What to do before the cold snap
- Walk your foundation on a bright day and look for daylight from inside the basement.
- Check the garage — the most common entry point we find on Long Island.
- Move food storage off the floor and into sealed containers.
- Cut the runway — trim shrubs back from the foundation and move woodpiles away from the house.
- Book an inspection in September, not November. Sealing an empty house is far cheaper than trapping a populated one.
If you're already hearing scratching in the walls, don't wait for it to get worse. A single pair of mice can produce dozens of offspring in a season, and the longer they nest, the more contamination and wire damage you're cleaning up later.