Pest control in Billings follows the short warm season in both directions. Ants, wasps, and the insects of the valley show up in those weeks, and mice move in when the weeks end. If you wait until the furnace is the warmest place in the house, you are meeting a problem that started at the foundation in the summer. Exclusion at the sill, the garage, and the eave is the work that should happen while you can still see the gaps. A spray on a pretty afternoon is not that work.
The rims and the fields meet yards on the Heights and the edges. Mice use those edges, plus any soffit the wind loosened. Wasps use porch ceilings. Ants use kitchens and damp basements after irrigation or a hard rain. Name what you saw. A nest, droppings, or wings are enough. Do not accept a plan that never names the animal. Spiders in a basement you live in are a separate complaint from a rodent trail along the rim joist. Say which one is in the room.
The warm season is short enough that people postpone and then discover the nest when they service the furnace. That is the wrong calendar. Schedule the closure before the cold locks everything against the concrete. Keep seed and pet food latched. A woodpile or a cottonwood stump against the wall is a bridge. If roof or siding work is happening while the weather allows, time the pest closure with it so a new soffit does not bury an open entry.
Say how many seasons the trail has repeated. One mouse and a population are different scopes. Houses that back to open bench ground have more pressure than a shaded south-side lot, and both still get visitors when a gap opens. Cleanup of droppings in the mechanical room belongs in the conversation if that is where they are living. The heating equipment should not be their closet. A photo beats a guess about the species.
Say the pest, the part of Billings, and whether you are still inside the warm season or already heating. Mention the foundation or the furnace room. Do not give them the winter to settle. Call the number on this page.