Rats don’t hibernate. When temperatures drop, they stay fully active and move to the warmest, most food-rich shelter they can find. For many rats, that means your home. Those that stay outdoors dig burrows deep enough to escape freezing temperatures, sometimes reaching several feet underground. Either way, rats are busy all winter long, eating, nesting, and reproducing just as they do the rest of the year.
Why Rats Get More Active in Fall
Rat activity actually peaks in November and the surrounding fall months, not in the dead of winter. As temperatures start to cool, rats shift from casually scavenging to aggressively stockpiling food. They’ll gather seeds, nuts, pet food, compost scraps, fabric, and even paper, transporting it all to a central stash near their nest. These caches are critical for feeding themselves and their young when food becomes scarcer.
This pre-winter push is when rats are most likely to find their way into buildings. They’re scouting for reliable warmth and food sources before conditions get harsh, so fall is the season when homeowners most often notice signs of new rodent activity.
Indoor Shelter: The Preferred Option
Given the choice between a cold underground burrow and a heated building, rats will pick your home every time. They’re remarkably good at getting inside. An adult rat can squeeze through a gap roughly the width of a quarter, about half to three-quarters of an inch in diameter. That’s small enough to fit through cracks around pipes, gaps beneath doors, openings where utility lines enter walls, or damaged vent covers.
Once inside, rats seek out warm, dark, low-traffic spaces. Their favorite indoor nesting spots include:
- Attics: Heat rises, making attics consistently warm. They also see little human foot traffic.
- Wall voids: The spaces between interior and exterior walls offer insulation and concealment.
- Crawl spaces and basements: These provide ground-level access and plenty of hiding spots.
- Areas near HVAC components or utility lines: Temperatures stay more consistent near heat-generating equipment.
Insulation is especially attractive. Rats shred it apart to build and reinforce nests, and the material itself traps body heat effectively. A rat nesting in fiberglass insulation near a warm light fixture or heating duct has created a surprisingly comfortable microclimate, even on the coldest nights. These enclosed spaces also shield them from predators and moisture, two threats that are just as dangerous as the cold itself.
How Outdoor Rats Survive Freezing Weather
Not all rats make it indoors. Plenty of colonies spend the entire winter outside, relying on burrows they’ve dug into the soil. Norway rats, the most common species in North America, are excellent diggers. A typical burrow runs 12 to 18 inches deep, but some extend as far as 4 feet underground, well below the frost line in many regions. At that depth, soil temperatures remain relatively stable even when the surface is frozen.
The layout of a burrow is strategic. Rats hollow out a den chamber near the middle section, positioned far enough from the entrance holes to buffer against temperature swings, wind, and moisture. Staying dry is essential. Wet fur loses its insulating ability quickly, so rats choose burrow locations that drain well and avoid flooding. They often dig alongside structures like walls, rocks, fences, or building foundations, which provide both structural support and some protection from the elements.
Vegetation plays a role too. Rats in temperate climates often burrow beneath evergreen plants, which block snow, rain, and wind from reaching the burrow entrance while providing shade in warmer months. When food runs low, outdoor rats will leave their burrows to forage, burrowing through snow if necessary, though they avoid it when they can.
Signs Rats Have Moved In
Rats are nocturnal and prefer to stay hidden, so you’re more likely to hear them than see them. Scratching or scurrying sounds in walls or ceilings at night are a classic sign, especially starting in late fall. Droppings are another reliable indicator: rat droppings are dark, pellet-shaped, and roughly the size of a raisin. You might also find gnaw marks on wood, plastic, or even electrical cables. Rats chew constantly to keep their teeth from overgrowing, and they’ve been observed burrowing under floorboards and chewing through wiring to access new areas of a home.
Grease marks along baseboards or walls are a subtler clue. Rats tend to follow the same paths repeatedly, and the oils in their fur leave dark smudges along these routes. Shredded insulation, fabric, or paper in attic corners or behind appliances points to active nest-building.
Keeping Rats Out Before Winter
The most effective strategy is sealing entry points before rats start looking for shelter in the fall. Focus on any gap or hole larger than half an inch. Common entry points include where pipes and wires penetrate exterior walls, gaps beneath garage doors, damaged soffit or fascia boards, uncovered vents, and cracks in the foundation.
Material choice matters. Rats can chew through rubber, plastic, soft wood, and standard spray foam without much effort. Steel wool packed tightly into gaps is one of the most effective and inexpensive solutions. For outdoor applications, copper mesh works the same way without rusting. In both cases, securing the mesh with caulk or rodent-resistant foam keeps it in place. Vents and crawl space openings should be covered with galvanized hardware cloth with a mesh size of a quarter inch or smaller. A chimney cap prevents entry from above.
Reducing food sources around your property also helps. Store pet food in sealed containers, keep compost bins secured, and clean up fallen fruit or birdseed. Rats are adaptable enough to eat nearly anything, so even small, consistent food sources can sustain a colony through winter.