San Diego Pest Activity Calendar: What's Active Every Month

Cool, wet weather keeps rodents sheltering in attics and garages. Winter rains raise moisture in crawl spaces; silverfish and roach activity follows the dampness.

Heavy rain floods Argentine ant colonies out of the soil and sends scouts indoors. The first big ant calls of the year usually follow February storms.

Warming soil wakes everything up. Carpenter ant swarmers appear near moisture-damaged wood, and spider populations begin their spring build.

Standing water from spring rains plus warming temperatures starts mosquito breeding, especially near lagoons, the San Diego River, and lake corridors. Gopher mound activity peaks with soft spring soil.

Pet and wildlife activity spreads fleas and ticks through canyons and yards. The May Gray marine layer keeps coastal homes damp enough for moisture pests to thrive.

Paper wasp and yellowjacket nests reach noticeable size. Aedes ('ankle-biter') mosquitoes get active in neighborhoods with any standing water.

Inland heat drives ants and crickets indoors chasing water, especially in El Cajon, Escondido, and Poway. Mosquito activity peaks countywide.

The largest ant invasions of the year hit in late summer as colonies chase water indoors. American cockroaches surge up drains in older neighborhoods.

Warm, still September days are classic drywood termite swarming weather in San Diego. Piles of shed wings on windowsills are the signature sign.

Mature orb weavers and black widows are at maximum size and visibility. Cooling nights start the fall rodent push into attics, the year's biggest exclusion season.

Rodent pressure on structures peaks as temperatures drop. Attic noise complaints spike this month across the county's canyon and grove neighborhoods.

Holiday cooking and warmth concentrate indoor pest activity in kitchens. Early winter rains restart the moisture-pest cycle in crawl spaces and garages.