Are There Mosquitoes in Washington?
Yes, mosquitoes are found throughout Washington State, though populations are most abundant in western regions and mountain valleys. The wet climate supports thriving populations. Peak activity runs from May through August, with some populations continuing into September. Coastal wetlands and river valleys are mosquito hotspots.
By Tim, founder of Easy Street Markets. I maintain the wildlife database and verify every animal and source myself. Updated July 22, 2026.
Pitcher-plant Mosquito · Michael and Antoni Hinczewski CC BY
Gallinipper · Meghan Cassidy CC BY-SA
Ornate Treehole Mosquito · Benjamin Burgunder CC BY
- 1,168
- GBIF records
Yes, mosquitos are in Washington. Next you'll want:
Yes, mosquitoes are found throughout Washington State, though populations are most abundant in western regions and mountain valleys. The wet climate supports thriving populations. Peak activity runs from May through August, with some populations continuing into September. Coastal wetlands and river valleys are mosquito hotspots.
Where in Washington Mosquitoes are Found
Mosquitoes occur throughout Washington State, from the Puget Sound lowlands to the Cascade Mountains and eastward. Populations are particularly abundant in western Washington due to the wet climate and numerous water bodies. The Willamette Valley extends into southern Washington and has dense populations. Puget Sound marshes and estuaries support specialized species. The Columbia River system and its wetland areas host populations. Eastern Washington has fewer mosquitoes overall but significant populations concentrate in river valleys, particularly along the Columbia River. Mountain valleys in the Cascades and Wallowa Mountains support seasonal populations. The Olympic Peninsula and Coastal Plain have high densities. Lakes throughout the state, including Lake Union, Lake Washington, and smaller alpine lakes, support populations. Wetland refuges including Ridgefield National Wildlife Refuge have particularly high mosquito densities. Urban areas from Seattle to Spokane have local populations. Learn more aboutWashington wildlife.
Season and Timing in Washington
Mosquito activity in Washington begins in April as temperatures warm and continues through September or October in most areas. Peak activity runs from June through August when warm temperatures coincide with sufficient moisture. Spring snowmelt in mountain areas creates abundant breeding habitat. Early summer rainfall in western Washington provides additional breeding sites. Western Washington, with its consistently moist climate, sees more sustained mosquito activity than eastern Washington. Eastern Washington has a more compressed season, beginning slightly later in May and ending in September. Mountain valleys experience shorter seasons tied to snowmelt. Some species have multiple generations per summer, creating sustained high densities. Fall frosts begin reducing activity in September. Winter temperatures are generally too cool for active mosquitoes, though some species survive winter in protected locations. TheWashington wildlifepage provides additional information about local fauna.
How to Identify Mosquitoes
Mosquitoes are small flying insects, typically 3 to 6 millimeters long, with a distinctive slender body and long needle-like proboscis. The body color ranges from gray to brown, often with subtle patterns of stripes or spots on the thorax and abdomen. The wings are long, narrow, and held flat along the body when at rest. The characteristic high-pitched whine comes from rapid wing beats during flight. Male mosquitoes have noticeably feathery antennae used to detect pheromones, while females have simpler antennae and a more prominent proboscis. Washington is home to approximately thirty mosquito species, though all share the same basic body plan. Some species are day-biters, while others are strictly nocturnal or crepuscular. Size and coloration vary slightly among species. The aquatic larvae are worm-like and quite different from the winged adults. Pupae are mobile and rest at the water surface.
Where Sightings Concentrate in Washington
Mosquitoes concentrate in and around standing water, their essential breeding habitat. Coastal and estuarine marshes in western Washington support the densest populations. Puget Sound marshes, particularly those in the central and southern regions, are major mosquito habitat. Rivers and backwater areas of the Columbia River and its tributaries have populations concentrated in slow-moving sections and adjacent wetlands. Lakes throughout the state attract females seeking egg-laying sites. Ponds, both natural and artificial, support populations. Wetland refuges and state parks often have high mosquito density during the active season. Mountain meadows with temporary pools from snowmelt support seasonal populations. Swamps and forested wetlands with standing water are particularly productive. Urban and suburban green spaces with poor drainage support populations. Stormwater retention ponds and roadside ditches become significant breeding sites. TheWashington wildlifeguide discusses habitat types.
Typical Mosquito Behavior
Mosquito behavior in Washington is driven by temperature and the need to find mates and blood meals. Males feed only on plant nectar and do not bite. Females require blood meals to produce eggs, which drives much of their activity. Most Washington species are crepuscular, most active during dawn and dusk, though some feed during the day and evening. Females use sensory receptors on their antennae and other parts of the head to detect carbon dioxide and body heat from potential hosts, often from distances of several hundred feet. Upon locating a target, they land and use their proboscis to penetrate the skin and find blood vessels. Mating occurs in flight or on resting surfaces, often in swarms. Eggs are laid on water surfaces or in damp substrates depending on species. The aquatic larval stage typically lasts five to fourteen days depending on water temperature. Pupae are non-feeding but mobile. Multiple generations can occur during Washington's long warm season.
Coexistence and Safety Notes
Mosquitoes have no legal protection status in Washington and are considered pests by most residents. The primary concerns are bite discomfort and potential disease transmission. West Nile virus is the main disease concern, transmitted by Culex mosquitoes, though transmission in Washington is generally uncommon. Most infected people experience no symptoms or mild illness. Severe cases are rare. Preventing bites is straightforward and effective. Use insect repellent containing DEET, picaridin, or oil of lemon eucalyptus when outdoors during peak hours. Wear loose-fitting light-colored long sleeves and pants, especially during dawn and dusk. Avoid being outside during peak activity hours if possible. Eliminate standing water around your home. Some areas conduct mosquito control spraying. Natural predators including dragonflies, damselflies, bats, and fish help keep populations in check. Consult thewildlifepage for more information.
Common Species People Confuse with Mosquitoes
Several small flying insects are mistaken for mosquitoes but belong to different families. Crane flies (family Tipulidae) are much larger and have extremely long, delicate legs. Midges (family Chironomidae) are very small and lack the long proboscis, though some males have feathery antennae. Fungus gnats are tiny dark flies with a distinctly hunched posture found in damp areas. Robber flies (family Asilidae) are predatory insects with a different body shape and hunting behavior. No-see-ums or biting midges (family Ceratopogonidae) are extremely small and barely visible without magnification. Drain flies are small dark flies with different wing pattern and silhouette. Horse flies and deer flies (family Tabanidae) are much larger. Gnats of various types may resemble mosquitoes in size but lack the distinctive long proboscis. The key identifying feature distinguishing true mosquitoes is the long, prominent feeding tube extending forward from the head, present in no other common flying insect.
Frequently Asked Questions
Are mosquitoes in eastern Washington as bad as western Washington? No, eastern Washington has fewer mosquitoes due to lower rainfall and lower humidity. Populations concentrate in river valleys and around water bodies. Why are some years worse than others? Spring rainfall and snowmelt affect populations. Wet years with heavy spring runoff see much higher mosquito densities than dry years. Do Washington mosquitoes carry diseases? West Nile virus is the primary concern, carried by Culex species. The risk is generally low, and most infected people have no symptoms or mild symptoms. What is the best way to avoid mosquitoes? Use insect repellent, wear protective clothing, avoid dawn and dusk, eliminate standing water, and camp away from water sources. Visit thewildlifepage for additional information about Washington fauna.
Plan your mosquito sighting in Washington
1,168 verified mosquito records have been logged in Washington, most recently in 2026. See the GBIF records.
Where to look in Washington
- Ebey's Landing National Historical Reserve · Wildlife Watching, Birdwatching · Find hotels
- Fort Vancouver National Historic Site · Wildlife Watching · Find hotels
- Lewis & Clark National Historic Trail · Wildlife Watching · Find hotels
- Lewis and Clark National Historical Park · Wildlife Watching, Birdwatching · Find hotels
- Mount Rainier National Park · Wildlife Watching, Birdwatching · Find hotels
- Nez Perce National Historical Park · Wildlife Watching, Birdwatching · Find hotels
More places to see mosquito
More wildlife in Washington