Why Rodents Enter Homes in Fall and Winter

Mice and rats are warm-blooded mammals that seek shelter when outdoor temperatures drop. In October and November, they actively seek warm places to overwinter — and residential structures provide the warmth, food, and nesting material they need. A mouse can enter through a gap the size of a dime (1/4 inch). Roof rats can enter through gaps in the roofline that most homeowners never think to check.

The Most Important Step: Seal Entry Points

This is the single most effective rodent prevention measure. Seal every opening larger than 1/4 inch (the size of a dime) around:

  • The point where the foundation meets the sill plate (the most common mouse entry point)
  • All gaps around utility penetrations — pipes, gas lines, electrical conduit, cable
  • Garage door bottom seal — even a small gap at the corner is sufficient
  • Gaps around dryer vent connections
  • Gaps at the roof line — vents, soffits, and where the fascia meets the siding
  • Gaps around HVAC conduit and refrigerant lines

Use steel wool embedded in caulk, hardware cloth, or metal flashing for permanent sealing — mice can chew through foam sealant alone.

Eliminate Attractants

  • Store all food in sealed hard-sided containers — including pet food. Paper and cardboard bags are not rodent-proof.
  • Keep garbage in sealed cans with tight lids.
  • Remove bird feeders in fall — fallen seeds are a prime rodent food source.
  • Stack firewood at least 20 feet from the home and 18 inches off the ground.
  • Trim vegetation away from the home — ground cover and dense shrubs provide cover for rodents approaching the foundation.
  • Remove standing water — rodents need water and are attracted to irrigation and low-lying moisture areas.

Early Warning Signs to Watch For

Check these areas monthly through fall and winter: under kitchen and bathroom sinks, inside the garage (especially along the walls), in the attic (listen for scratching at night), and in any storage areas. Finding droppings early means catching an infestation before it multiplies.

✓ Schedule a professional entry point inspection in September or October — before fall entry season peaks. A trained eye identifies gaps that homeowners typically miss, and professional sealing is more permanent than DIY foam.