Winter Pest Guide for North Bay California

Subterranean Termite Swarm Season Begins

Winter rain events in the North Bay trigger subterranean termite swarming — mature colonies use rain as a signal that soil conditions are favorable for establishing new colonies. Subterranean termite swarmers (dark brown-black, with white equal-length wings) emerge in large numbers, often appearing inside structures through foundation gaps, and are commonly seen near windows and light fixtures following rain. If you observe a termite swarm inside your home in winter, call for inspection immediately — this indicates a mature colony established within or immediately adjacent to the structure.

Rodent Pressure — Peak Indoor Season

December through February is the peak season for indoor rodent activity in the North Bay. Established attic infestations are at maximum density, having recruited throughout fall. Noise in attic or walls at night, droppings, and gnaw damage are most commonly reported in this period. Winter is also when wiring damage from rodent gnawing most frequently creates fire hazards, as dry winter conditions in attics create fire risk from damaged insulation and wiring.

Crawl Space Moisture — Peak Risk Period

Winter rain saturates soil and raises groundwater, creating the elevated crawl space moisture conditions that are the primary driver of subterranean termite activity and wood-decay fungus growth in North Bay homes. If your crawl space has inadequate vapor barrier, poor ventilation, or drainage issues, winter is when these conditions are most damaging. A crawl space inspection in mid-winter accurately identifies the moisture conditions that drive structural pest activity year-round.

Winter Pest Priorities

• If you observe termite swarmers inside after a rain event, call for inspection immediately
• Check attic for signs of rodent activity — droppings, gnaw marks on rafters, compressed insulation trails
• Inspect the crawl space or have it professionally inspected for moisture accumulation and subterranean termite mud tubes
• Address plumbing drips and drainage issues that become apparent during heavy rain — moisture is the common thread for winter pest activity
• Plan and schedule your spring termite inspection early — January and February are good low-pressure scheduling months before the spring rush

Frequently Asked Questions