By Integrity Rodent Proofing, Dixon, California. Updated October 2026
Key takeaways
- Fall is when rats and mice move in. Cooler nights, outdoor food running out, and the first rains push them toward warm, dry shelter, and a house is the best option around.
- This year has an extra push: a very strong El Niño is forecast for this fall and winter, and wet weather drives rodents out of flooded ground cover and into structures.
- The openings they use are small: a rat needs about a quarter-size gap, a mouse about a quarter inch. They are at the roofline, vents, garage corners, and where pipes and lines enter the house.
- Sealing the openings keeps new rodents out, and trapping removes the ones already inside. Fall is the cheapest time to do it, before they are settled in for winter.
Why fall, and why this fall is different
Summer is breeding season outdoors, so rodent numbers peak as the weather turns, and harvest pushes field rodents toward the nearest buildings. A strong El Niño is forecast this winter. Rain drives Norway rats out of flooded low ground and roof rats down from soaked trees to the roofline.
The fall checklist: start at the roofline
Walk the roofline from the ground. Look for gaps at eaves, coves, and roof-to-wall joints, and for vent screens loose, torn, or missing. Most rat entries start up high. Screens must be intact and secured, and the vent still has to vent. Trim branches back and move firewood away from the walls.
Hearing scratching? Finding droppings?
Let's find out how they're getting in.
An entry-point inspection checks the common ways rats and mice get in, shows you what we find, and tells you what needs to be sealed.
The fall checklist: doors, pipes, and food
Fix the garage corners. Gaps at the bottom corners of a garage door are the most common mouse entry we see. Check the bottom seal too. Look where pipes and lines enter: gaps around them run into wall voids and up to the attic. Pick up fallen fruit, and keep pet food and birdseed in hard-sided containers with lids.
If rodents are already inside
Seal first anyway. We seal the openings so no more can get in, then trap the ones still inside until the activity stops.
Signs they are already in
Night scratching in the ceiling. Droppings along attic beams or in the garage. Gnaw marks. Dark rub marks along beams and pipes. Fruit eaten out to the rind. Any one of these in October means they are already in.
How Integrity works
Our inspections are free, and we offer same-week inspections. We check the roofline, attic, garage, crawlspace, and outside of the home, show you the openings we find, and give you a written estimate before any work begins. We are licensed and insured, and we do not use poison. We serve Dixon, Davis, Woodland, Winters, Vacaville, West Sacramento, Sacramento, Roseville, Folsom, Fairfield, Citrus Heights, Carmichael, and American Canyon. Call (707) 754-2408, Monday to Saturday, 9am to 6pm.
Common questions
When does fall rodent season start in Northern California?+
With the first cool nights, usually October, when homeowners here start hearing scratching and finding droppings.
Does a wet El Niño winter really mean more rats in houses?+
More pressure, not a guarantee for any one house. Rain floods burrows, so rodents look for dry shelter. Getting in comes down to your openings.
Can I just do the checklist myself?+
Yes, especially the fruit, firewood, and food storage steps. Roofline gaps and vent failures are hard to see from the ground.
I am already hearing scratching. Is it too late for fall proofing?+
No. Seal the openings first, then trap the rodents still inside.
Do you use poison?+
No. We seal and trap.
Written by
The Integrity Rodent Proofing team
Dixon, California. Rodent-proofing specialists serving Dixon, Davis, Woodland, Winters, Vacaville, West Sacramento, Sacramento, Roseville, and Folsom. We find how rats and mice are getting in, explain what we find, and seal the openings.