Washington State is home to two main rat species that cause problems for residents: the Norway rat and the roof rat. Both thrive in the state’s mild, wet climate, and Seattle currently ranks 17th on Orkin’s 2025 list of the worst U.S. cities for rats. Whether you’re dealing with an active infestation or trying to prevent one, here’s what you need to know about rats across the state.
Species You’ll Find in Washington
Norway rats are the more common of the two. They’re stocky, brownish-gray, and prefer ground-level living. You’ll find them burrowing under foundations, in basements, crawl spaces, and along sewer lines. They’re strong swimmers and often enter homes through damaged drains or gaps in foundations. An adult Norway rat can squeeze through an opening the size of a quarter.
Roof rats are sleeker, darker, and better climbers. They favor attics, rafters, and trees, and they’re especially common in western Washington where dense vegetation gives them easy routes onto rooftops. If you hear scratching overhead at night, roof rats are the likely culprit. Both species are active year-round in Washington, but activity spikes in fall when cooling temperatures push them to seek shelter indoors.
It’s worth noting that the deer mouse, while not a rat, is another rodent of serious concern in Washington. Deer mice are the primary carrier of hantavirus in the state, and they’re found in every part of it.
Health Risks From Rats and Rodents
Rats in Washington can transmit several diseases. They contaminate food and surfaces with their droppings, urine, and saliva, and they can spread leptospirosis (a bacterial infection that causes fever, muscle pain, and in severe cases kidney or liver damage), salmonella, and rat-bite fever.
The most dangerous rodent-borne disease in Washington is hantavirus pulmonary syndrome, carried by deer mice. The Washington Department of Health reports one to five cases per year, and roughly one in three people diagnosed with it have died. You can be exposed simply by breathing in dust contaminated with mouse droppings, urine, or nesting material. Symptoms appear one to eight weeks after exposure and start with fever, sore muscles, headaches, nausea, and fatigue. Within a few days, the disease progresses to severe shortness of breath as fluid fills the lungs, and hospitalization is almost always required.
This is why cleaning up rodent droppings safely matters so much. Never sweep or vacuum droppings dry. Instead, soak the area with a bleach solution (one part bleach to ten parts water), let it sit for at least five minutes, then wipe up with paper towels and dispose of everything in a sealed bag. Wear rubber gloves and, if you’re cleaning an enclosed space like a shed or cabin that’s been closed up, a respirator rated for particulates.
Keeping Rats Out of Your Home
The most effective long-term strategy is exclusion: physically blocking every route rats use to get inside. Rats need surprisingly small openings. Inspect your foundation, where utility pipes and wires enter the building, vents, crawl space access points, and the roofline. Seal gaps with steel wool stuffed into the opening and covered with caulk, or use metal flashing for larger holes. Rats chew through wood, plastic, and even low-grade concrete, but they can’t get through steel.
Beyond sealing entry points, reduce what attracts them in the first place. Store pet food and birdseed in sealed metal or heavy plastic containers. Keep garbage cans tightly lidded. Pick up fallen fruit from trees. Move woodpiles and dense vegetation away from the house. Compost bins are a common attractant, so use enclosed tumbler-style composters rather than open piles. Trim tree branches so they don’t touch or overhang the roof, cutting off the highway roof rats use to reach your attic.
Inside, fix leaky pipes and eliminate standing water. Rats need water daily and will stay close to a reliable source. Clean up food debris promptly and store pantry items in containers rats can’t gnaw through.
Trapping and Rodenticide Rules
Snap traps remain the most straightforward option for homeowners. Place them along walls, behind appliances, and near droppings or gnaw marks, with the trigger end facing the wall. Peanut butter is a reliable bait. Check traps daily. For a serious infestation, you may need a dozen or more traps set simultaneously, because catching one or two at a time rarely outpaces a breeding population.
If you use rodenticide (rat poison), Washington has specific regulations. All outdoor, aboveground bait must be placed inside locked, tamper-resistant bait stations. Bait cannot be placed anywhere accessible to children, pets, or non-target wildlife. Loose bait can’t go on shelves, counters, or ledges, though it can be placed on attic floors. Every bait station must be clearly labeled with the applicator’s name, contact information, and the product’s active ingredients. When a baiting operation is complete, any remaining bait that could be accessed by the public must be recovered and disposed of according to the label.
These rules exist because rat poisons pose serious risks to pets, children, and wildlife like owls and hawks that eat poisoned rodents. Many pest control professionals in Washington now emphasize an integrated approach: exclusion first, traps second, and rodenticides only as a last resort.
Landlord and Tenant Responsibilities
If you’re renting in Washington, the law is clear on who handles rat problems. Under the state’s landlord-tenant guidelines, landlords must control mice, rats, and other pests before a tenant moves in. After move-in, the landlord remains responsible for pest control in multi-unit buildings. The only exceptions are single-family homes or situations where the tenant’s own behavior caused the infestation, such as leaving garbage or food waste unsecured. In those cases, the tenant pays for pest control.
If your landlord isn’t responding to a rodent complaint, document the problem with photos of droppings, damage, or entry points, and submit your request in writing. Washington tenants have legal standing to pursue remedies if a landlord ignores a habitability issue, and an active rat infestation qualifies.
Where Infestations Are Most Common
Urban areas along the I-5 corridor, particularly Seattle, Tacoma, and Olympia, see the highest concentration of rat complaints. Seattle’s combination of older housing stock, dense neighborhoods, mild winters, and abundant food waste from restaurants creates ideal conditions. The city’s infrastructure also plays a role: aging sewer systems give Norway rats underground networks to travel through.
But rats aren’t just an urban issue. Rural properties across Washington deal with them too, especially farms with grain storage, livestock feed, and outbuildings that provide shelter. In eastern Washington, where winters are harsher, rats are more seasonal in their push indoors, but once they establish themselves in a barn or crawl space, they breed quickly. A single pair of Norway rats can produce up to 12 litters a year, with six to twelve pups per litter. Without intervention, a small problem becomes a large one within months.