Pests to know in Seattle
Termites in Seattle
WSU says the region has two native termites: the dampwood termite and the subterranean termite.[1]
Pests local experts flag
- WSU says Washington has two main rat species, the Norway rat and the roof rat. Roof rats are better climbers and nest in trees, attics and walls.[4]
- WSU names the house mouse and the deer mouse as Washington's main problem mice and notes that deer mice are a primary carrier of hantavirus.[4]
- Public Health – Seattle & King County says West Nile virus was first found in King County in 2006 and is now established in Washington state.[5]
Climate
Central Seattle (ZIP 98104) is in USDA plant hardiness zone 9a, where the average coldest winter night is 20 to 25°F.[7]
Public agencies that handle pests
Public Health – Seattle & King County responds to rodent complaints and in some cases enforces the King County Board of Health's Title 8 rodent control rules.[2]
Hiring a licensed company
The state pesticide regulatory agency for Washington is the Washington State Department of Agriculture (Pesticides and Fertilizers), which oversees pesticide applicator certification and licensing.[8]
Free local help
WSU King County Extension in Renton runs programs including Master Gardeners, 4-H, SNAP-Ed and forest stewardship for King County residents.[3]
Through the year
- Spring to Fall
- WSU says dampwood termites swarm in late summer or fall, especially after rain, while subterranean termites may swarm at any time of year.[1]
- Spring to Summer
- WSU says carpenter ant mating swarms generally happen from April to early June, and calls the ants a structural pest because they dig nests in wood.[6]
Sources
- Washington State University PestSense, “Termites.” pestsense.cahnrs.wsu.edu/fact-sheet/termites/ (accessed 2026-10-06)
- Public Health – Seattle & King County, “File a rodent complaint.” kingcounty.gov/en/dept/dph/health-safety/environmental-health/getting-rid-of-rats-mice/file-rodent-complaint (accessed 2026-10-06)
- Washington State University Extension, “King County Extension.” extension.wsu.edu/king/ (accessed 2026-10-06)
- Washington State University PestSense, “Mice and rats.” pestsense.cahnrs.wsu.edu/fact-sheet/mice-and-rats/ (accessed 2026-10-06)
- Public Health – Seattle & King County, “Mosquitoes.” kingcounty.gov/en/dept/dph/health-safety/disease-illness/zoonotic-diseases/diseases-by-animal/mosquitoes (accessed 2026-10-06)
- Washington State University PestSense, “Carpenter ants.” pestsense.cahnrs.wsu.edu/fact-sheet/carpenter-ants/ (accessed 2026-10-06)
- USDA ARS and PRISM, via phzmapi.org, “Plant hardiness zone for ZIP 98104 (2023 USDA map data).” phzmapi.org/98104.json (accessed 2026-10-06)
- National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)