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Kansas · Mosquito Season Guide

Is it mosquito season in Kansas?

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II. Kansas Mosquito Season Month by month

Kansas ranks among the most West Nile Virus-active states in the nation year after year. The combination of warm summers, extensive agricultural irrigation, and two major river systems creates ideal conditions for Culex tarsalis — the primary WNV vector. Sedgwick County (Wichita) and the Kansas City metro area consistently lead the state in annual case counts.

Wichita / South-Central KS
Wichita · Derby · Hutchinson
Kansas City / Eastern KS
Overland Park · Kansas City · Topeka
Very Low Low Moderate High Very High taller = more active · color = severity
~50
mosquito species recorded in Kansas
May–Oct
active season statewide
Top 10
nationally for West Nile Virus cases most years
105
counties — all with seasonal exposure

Wichita and south-central Kansas: the WNV epicenter

Sedgwick County has historically been one of the most WNV-active counties in the US during high-transmission summers. The Arkansas River corridor, the city's irrigation and drainage infrastructure, and warm summer temperatures combine to sustain enormous Culex tarsalis populations through July and August. The county runs an aggressive spray program but still records significant human cases most years.

The Kansas City metro: urban pressure

The eastern Kansas portion of the Kansas City metro — Overland Park, Olathe, Lenexa — experiences intense Culex pipiens pressure in residential areas alongside Culex tarsalis in surrounding agricultural zones. The Kansas and Missouri rivers create extensive floodplain habitat. Johnson County runs one of the state's more active county vector control programs.

Western Kansas: agricultural intensity

The high plains counties of western Kansas — irrigated by center-pivot systems drawing from the Ogallala Aquifer — produce substantial Culex tarsalis habitat in the spray irrigation runoff and drainage sumps. Finney, Ford, and Grant counties see significant WNV pressure in high-activity summers despite relatively sparse human population.

III. Kansas's Key Mosquito Species
Culex tarsalis mosquito photograph
Culex tarsalis
Western Encephalitis Mosquito

The engine of Kansas's perennial West Nile problem. Sedgwick County's status as one of the nation's most WNV-active counties is a Culex tarsalis story — the Arkansas River corridor through Wichita provides exactly the warm, slow, agricultural water this species exploits. During the catastrophic 2003 WNV season, Kansas recorded over 600 human cases, with the Arkansas River valley as the epicenter. Center-pivot irrigation in western Kansas creates tarsalis habitat across vast stretches of the high plains that would otherwise be inhospitable — runoff from spray irrigation sustains breeding through dry summers.

Culex quinquefasciatus mosquito photograph
Culex quinquefasciatus
Southern House Mosquito

The urban WNV vector that operates in Wichita, Overland Park, Topeka, and Kansas City while tarsalis dominates the surrounding farmland. Culex quinquefasciatus is more heat-tolerant than pipiens and thrives in the warm, organically enriched water of Kansas's urban drainage infrastructure — storm drain sumps, catch basins, the sluggish lower reaches of urban creeks. It is the dominant species in Wichita neighborhoods south of the Arkansas River, where it drives the highest urban WNV transmission rates in the state most summers.

Aedes albopictus mosquito photograph
Aedes albopictus
Asian Tiger Mosquito

Established in eastern Kansas and advancing steadily westward along the Missouri River corridor. The tiger mosquito has reached as far west as Salina in recent surveillance, and is firmly established throughout the Kansas City metro, Topeka, and the I-70 corridor. Unlike the Culex species that dominate Kansas's WNV story, Ae. albopictus bites aggressively during daylight and breeds in small containers — extending biting pressure into hours and habitats where residents don't expect it.

IV. Kansas Cities at a Glance
CityPeak SeasonOff-SeasonNotes
Wichita May – Oct Off Nov–Apr Sedgwick County; historically one of highest WNV counties in US; Arkansas River corridor Check live
Overland Park May – Oct Off Nov–Apr Johnson County; suburban container habitat; Kansas River floodplain proximity Check live
Kansas City May – Oct Off Nov–Apr Kansas/Missouri River confluence; floodplain habitat; county spray program active Check live
Topeka May – Oct Off Nov–Apr Kansas River corridor; Shunganunga Creek; above-average urban pressure Check live
Olathe May – Oct Off Nov–Apr Johnson County; fast-growing suburb; new development creates standing water habitat Check live
More State Guides
Florida Year-round activity in the south — 80+ species including invasive Ae. aegypti and the Asian tiger mosquito across all 67 counties Texas ~85 species across four climate zones — Gulf Coast active March through November, with year-round pressure in the Rio Grande Valley California Central Valley is the #1 West Nile corridor in the US — invasive Ae. aegypti and Ae. albopictus now established in 20+ counties Georgia Atlanta metro leads the Southeast in Asian tiger mosquito density — active statewide March through November New York Ground zero for West Nile in the US (1999 Queens outbreak) — NYC metro and Long Island see the highest Northeast seasonal pressure Illinois Home of the 2002 Cook County West Nile outbreak — the deadliest urban WNV event in US history — peak season June through September Ohio Lake Erie to the Ohio River — WNV active in Franklin and Cuyahoga counties, with floodwater species surging after summer storms Pennsylvania Philadelphia WNV corridor meets rural EEE risk in western PA — the densest human population in the mid-Atlantic mosquito belt Michigan Site of the 2019 EEE outbreak — the deadliest in decades — 10 human cases and 6 deaths concentrated in SW Michigan Great Lakes wetlands New Jersey Oldest organized county mosquito control in the US (1914) — Pine Barrens EEE corridor and fierce salt marsh Shore species Virginia Tidewater season runs April–October — the longest mid-Atlantic window — with the Great Dismal Swamp as an active EEE hotspot North Carolina The coastal plain runs one of the longest seasons in the Southeast — NC leads the nation in La Crosse encephalitis cases from the Appalachian foothills Maryland Chesapeake Bay watershed creates extraordinary mosquito habitat — tidal marshes, Eastern Shore wetlands, and the DC-Baltimore corridor combine for dense seasonal pressure Tennessee Memphis and the Mississippi River corridor historically record the highest WNV case counts in the mid-South — Ae. albopictus has colonized all 95 counties Indiana Indiana sits at the crossroads of the Great Lakes EEE belt — Lake Michigan wetlands in the north and the Wabash River floodplain drive intense seasonal pressure Louisiana The Gulf Coast's most intense pressure — coastal marshes and summer rains keep Cx. quinquefasciatus and Ae. aegypti active from March through November Alabama Mobile Bay to the Tennessee Valley — Ae. albopictus has reached all 67 counties and peak WNV season runs June through September South Carolina Low Country marshes produce some of the Southeast's densest Anopheles and Culex populations — season runs March through November Minnesota 10,000 lakes means 10,000 breeding sites — the Northwoods sees intense but short July–August peaks, while the Twin Cities face a longer June–September window Wisconsin Great Lakes wetlands and the Mississippi River backwaters drive strong WNV pressure in the Milwaukee corridor — peak season July through August Missouri At the confluence of the Missouri and Mississippi rivers — St. Louis historically ranks among the highest WNV cities in the US — season May through October Arkansas Delta rice-field flooding and the Arkansas River bottomlands create some of the highest rural mosquito pressure in the mid-South — active April through October Washington Western WA stays mild and damp year-round; the Yakima Valley and Columbia Basin face the highest WNV risk in the Pacific Northwest — peak July through September Arizona Monsoon season (July–September) drives sudden mosquito explosions across the Valley of the Sun — WNV detected annually Colorado Front Range WNV corridor stretches Denver to Fort Collins — eastern plains carry the state's highest risk Connecticut Connecticut River valley WNV pressure meets EEE risk in inland freshwater wetlands — active May through October Delaware Chesapeake and Delaware Bay marshes create outsized pressure for the nation's second-smallest state Hawaii Year-round activity at sea level — no native species, but Ae. aegypti and tiger mosquitoes established statewide Idaho Snake River Plain irrigation districts fuel summer WNV pressure — season June through September Iowa Mississippi River corridor and prairie wetlands drive intense June–September pressure — WNV active statewide Kentucky Ohio River corridor and Kentucky Lake wetlands sustain a long April–October season across all 120 counties Maine Short but intense July–August season — EEE detected in some years in the southern coastal plain Massachusetts EEE fatality rate exceeds 30% — the Plymouth County swamp complex is the active epicenter — season May through October Mississippi Gulf Coast near-year-round pressure meets Delta rice-field flooding for one of the South's most intense mosquito environments Montana Yellowstone and Missouri River corridors drive a compressed June–August season — WNV detected most years in eastern MT Nebraska Platte River valley and eastern Nebraska are among the Great Plains' most active WNV zones — peak July–August Nevada Las Vegas monsoon season drives July–September activity; Reno irrigation districts fuel a parallel northern peak New Hampshire EEE detected most years — the southern lakes and coastal plain are in the active Northeast EEE corridor New Mexico Monsoon season (July–September) creates sudden breeding habitat; WNV circulates in the Rio Grande valley annually North Dakota Red River Valley flooding produces some of the Great Plains' most extreme floodwater mosquito events — peak June–August Oklahoma One of the South-Central's most intense seasons — the Arkansas and Red River corridors sustain populations April through October Oregon Eastern Oregon Columbia Basin is the state's WNV hotspot; western Oregon runs a mild coastal season June through September Rhode Island New England's densest coastal pressure — Narragansett Bay salt marshes and WNV active in all five counties South Dakota Missouri River and James River valleys drive summer WNV activity — eastern SD sees the most intense pressure Utah Salt Lake Valley WNV corridor and irrigation districts sustain a July–September peak — drier areas see limited activity Vermont Champlain Valley runs Vermont's longest season — EEE detected in the Lake Champlain lowlands in some years West Virginia Kanawha and Ohio River valleys sustain a May–October season — Ae. albopictus now established statewide Wyoming The shortest meaningful season of any contiguous US state — North Platte valley WNV window is just 6–8 weeks
West Nile, dengue, and EEE: US disease risk by region → Asian tiger mosquitoes: why you're getting bitten during the day → Eliminating standing water: the highest-leverage yard move →