Every year, right around the first real cold snap and the start of the rains, our phones get busier. It’s not a coincidence: fall is rodent season in the North Bay, and the same things that make Sonoma, Napa, and Marin beautiful — vineyards, orchards, oak woodlands, open space — are exactly what produces large, healthy rodent populations that start looking for winter shelter in October and November.

Why fall pushes rodents into homes

Three things happen at once in our region every autumn:

• Food disappears outdoors. Harvest wraps up, grasses dry out and die back, and the easy calories rodents relied on all summer vanish.
• Temperatures drop. Rats and mice don’t hibernate — they need warm shelter to keep breeding through winter, and an attic or sub-level is perfect: dry, insulated, and undisturbed.
• The landscape gets disturbed. Crush season activity, vineyard maintenance, field mowing, and construction all flush established rodent populations out of their summer habitat and send them looking for new harborage — often the nearest structure.

Properties that border vineyards, orchards, creek corridors, or open space feel this first and hardest — which describes a large share of homes in our four counties.

Why “wait and see” is expensive

A pair of mice that moves into your attic in October can become a full colony by spring. Over one winter, rodents can contaminate insulation, chew through HVAC ductwork, gnaw wiring, and soil a sub-level vapor barrier — turning what would have been a straightforward exclusion job into a restoration project. The cheapest rodent problem is always the one you catch before it settles in for the season.

Your fall prevention checklist

These are the same items we check on inspections — and most homeowners can run through the basics in an afternoon:

1. Walk the perimeter. Look for gaps where pipes, wires, and vents enter the house. Remember: a mouse needs only ¼ inch, a rat about ½ inch.
2. Check foundation and attic vents. Screens should be intact, fitted, and made of rodent-proof metal — not lightweight insect screen.
3. Inspect door sweeps and garage door seals. If you can see daylight, a rodent can get in.
4. Trim vegetation. Tree branches touching the roof are highways for roof rats; dense ivy and shrubs against the foundation provide cover right at the wall line.
5. Move firewood away from the house and elevate it off the ground.
6. Secure food and seed. Pantry goods, pet food, and birdseed belong in sealed containers — including in the garage.
7. Fix moisture problems. Leaky spigots, poor drainage, and damp sub-levels attract rodents and the insects they feed on. A sealed sub-level with a proper vapor barrier removes both the moisture and a major entry route.
8. Listen at night. The earliest warning sign of fall invasion is usually sound: scratching or scurrying in the ceiling or walls after dark.

The two things you can’t DIY

First, a trained eye: entry points like roof returns, construction joints, and sub-level penetrations are easy to miss if you don’t inspect houses for a living. Second, proper exclusion materials: expanding foam and steel wool from the hardware store are temporary at best — rodents chew through or around them. Professional exclusion uses metal mesh, flashing, and sealants that hold up.

Get inspected before the rains

The best time for a rodent inspection is now, before winter occupancy is established. Our $350 inspection covers the entire property — roofline, foundation, attic, and sub-level — with photo documentation and a written plan. Move forward with the work and the fee is credited and matched: $700 toward your project, backed by a 1-year guarantee and a 6-month follow-up inspection. Serving Sonoma, Napa, Marin, and Solano counties. Call (707) 978-6024 (Napa/Sonoma) or (415) 740-5170 (Marin/S.F.) to schedule before the season peaks.