What a 16F winter actually does to the problem
Severe cold does not solve a rodent problem. It concentrates one, and understanding that changes how you spend money on it. When outdoor lows average 16F, a heated building stops being one option among many and becomes the only workable place to spend the season. That is why the autumn move in Milwaukee is so abrupt compared with milder cities: animals are not drifting in over months, they are arriving in a matter of weeks as the ground hardens. Once inside, they are insulated from everything you might have hoped would help. A wall cavity beside a heated room holds a steady temperature, condensation on cold surfaces supplies water, and nothing hunts them. Breeding continues through the coldest weeks of the year. Meanwhile the ground outside freezes, which means the exterior half of the work becomes physically harder to do. That is the argument for timing. The same list of repairs, done in late August, costs less effort and prevents the arrival entirely. Done in January, it is performed on frozen soil around a building that already has residents, and it has to be paired with trapping to be worth anything. If you are reading this in summer with a minor problem, that is the moment worth using.
Frost, heave and the gaps that open every year
One of the reasons a house that was sealed two winters ago has mice again is that buildings here move. Repeated freezing and thawing lifts slabs, shifts steps and works at mortar joints. A garage slab pulls away from the frame by a fraction of an inch. A concrete stoop rises and leaves a gap where it meets the wall. A door frame racks slightly and the bottom corner opens. None of these are dramatic, and all of them are wider than a quarter inch, which is the only measurement that matters. So exclusion in this climate is not entirely a one-time job. The metal you install stays put, but the building around it keeps changing shape, and each freeze cycle offers a new candidate opening. The practical response is a yearly walk-around in early autumn, before the move indoors. You are looking for daylight and fresh gaps at the same short list of places: slab edges, door bottoms, the seam where a stoop or porch meets the wall, and any spot where a utility line passes through below grade. Ten minutes with a flashlight in September saves a winter of trap checks, and the repairs are usually small enough to handle with a piece of hardware cloth and a few screws.
The garage is the building nobody seals
Rodent plans tend to stop at the house, and in this climate that leaves the most popular building on the property untouched. An unheated garage is not warm, but compared with open ground in a Milwaukee January it is an enormous improvement: dry, sheltered from wind, and usually full of exactly what a rodent needs. Bags of birdseed, ice melt and pet food sit at floor level. Stacked cardboard shreds into bedding. Boxes against the wall create a protected run from one end to the other. Work it as a separate structure with its own list. The service door needs a metal sweep, the overhead door needs an intact bottom seal, the slab edge needs checking for frost gaps, and stored feed needs hard containers rather than the sacks it came in. Getting boxes up onto shelves removes the covered runway and makes any remaining activity visible. If money is tight, the garage is often the best-value part of the whole job, because the repairs are simple and the sanitation gains are large. A house sealed while the garage stays open just means the animals are next door, and twenty feet is nothing to them.
Reading the evidence before you spend anything
Before you buy products or book a visit, spend an hour working out what you actually have. It changes the plan more than any product choice will. Start with droppings, because they answer species and age at once. Pointed ends on something the size of a rice grain says mouse. Blunt ends on a pellet several times that size says rat. Fresh droppings are dark and slightly soft; old ones are grey, dry and crumble under a tool. A pile of grey droppings and nothing new tells you a different story than a scattering of fresh ones. Then map where they are. Droppings concentrated in one cupboard suggest a nest close by. Droppings strung along a wall base suggest a travel route, and travel routes lead somewhere worth finding. Finally, go outside with a flashlight at ground level. You are looking for smooth openings two to three inches across in soil, runways worn through grass or mulch, and gaps under doors. Finding a burrow changes the job from a sealing job into a sealing plus exterior job, and it is far better to know that before someone quotes you rather than after the first month of traps.
Questions that separate a plan from a subscription
Two proposals can carry similar prices and deliver completely different outcomes, so ask about the work rather than the total. Ask whether the openings are listed individually with a material named for each. A quote that says exclusion as one line cannot be checked once the crew has gone, and it usually means less work than you assumed. Ask whether the garage is included. In this city that single question can move a price more than anything else on the page, and it is the item most often quietly left out. Ask how many return visits are in the price, what triggers an extra charge, and what happens if you hear activity again in six weeks. Trapping with no return dates attached is not a schedule, it is an intention. Ask what goes outdoors, where it sits, and how pets and other animals are kept away from it. And ask what the provider expects the building to look like when the work is finished, because a good answer describes closures you can point at. The cheaper number is frequently a monthly station service that leaves the house exactly as it was, which in a climate this cold means paying every month for a problem that was never repaired.