Yes, rats do move indoors during cold weather. When temperatures drop, rats actively seek out warmer, sheltered places to survive. Your home or any building becomes especially appealing to them because it offers warmth, protection from predators, and, often, easy access to food and water.

In New Hampshire, rat movement indoors typically begins when outdoor overnight temperatures consistently fall below 40°F — usually late September to mid-October in southern NH, and as early as early September in the North Country. By November, outdoor temperatures make survival increasingly difficult and indoor migration is at its peak.

Why Rats Enter Homes in Cold Weather

Rats are warm-blooded mammals, just like us, and they cannot withstand prolonged exposure to harsh cold. In their natural environments — fields, sewers, or outdoor nests — food becomes scarce, and the weather can be life-threatening. This cold season survival pressure pushes rats to look for shelter inside homes, garages, sheds, or any structure that can offer insulation and a stable temperature.

How Rats Get Indoors

These rodents are incredibly resourceful and agile. Rats can squeeze through openings as small as a quarter (about 0.6 inches or 1.5 centimeters wide). They use any available gaps: cracks in the foundation, holes near pipes, spaces under doors, damaged vents, and access points around windows. They can also climb rough surfaces, jump several feet, or even swim up sewer pipes to make their way inside.

NH's freeze-thaw cycles are particularly important for rat entry: repeated freezing and thawing of soil and mortar throughout the winter gradually opens new gaps in older foundations. Inspect your foundation for new cracks each spring and seal before the following fall rodent season.

What Attracts Rats Inside

• Warmth: Rats are driven by the need to stay warm and will find heated spaces, like attics, basements, and wall voids, especially attractive in winter.
• Food sources: Unsealed food containers, pet food bowls, garbage cans, or even crumbs can lure rats indoors. If they find abundant food, they are likely to build nests nearby.
• Water: Leaky pipes, condensation, and pet water bowls are all sources that can sustain rats once they are inside.

Signs That Rats Have Moved Indoors

• Droppings: Small, dark, rice-shaped feces often left along walls or in cupboards.
• Gnaw marks: Rats must gnaw constantly to keep their teeth from growing too long. Look for chewed wood, wires, or packaging.
• Noises: Scratching, scampering, or squeaking sounds in walls, ceilings, or basements, especially at night.
• Nesting material: Shredded paper, fabric, or insulation used to build nests.

How to Prevent Rats From Entering During Cold Weather

Preparation should happen before migration begins:

• August–September — inspect and seal exterior entry points
• Early October — set perimeter traps or bait stations
• Mid-October through March — active monitoring period

Waiting until you see rats indoors means they've already established.

• Seal all entry points: Inspect your home for cracks, gaps, or holes and seal them with steel wool, metal sheeting, or caulk.
• Store food securely: Keep all food — including pet food — in airtight containers, and clean up crumbs and spills quickly.
• Remove clutter: Get rid of piles of boxes, paper, and unused materials that rats could use for nesting.
• Fix leaks and excess moisture: Repair dripping pipes or leaky faucets and avoid leaving standing water in sinks, pet bowls, or trays.
• Regular inspections: Check attics, basements, and crawl spaces regularly, especially as temperatures begin to drop.

What to Do if Rats Move Into Your Home

If you notice any signs of rats, it's important to act quickly. Rats breed rapidly, so a small problem can turn into a large infestation in a short time. For minor issues, snap traps placed along walls where you notice activity may be effective. For larger infestations, or if you're uncomfortable handling the problem yourself, hiring a professional pest control service is the safest and most effective solution. They can also help you identify how rats are getting in and prevent future problems.

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