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Nebraska · Mosquito Season Guide

Is it mosquito season in Nebraska?

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II. Nebraska Mosquito Season Month by month

Nebraska is one of the most persistently active West Nile Virus states in the nation — the Great Plains combination of warm summers, irrigated agriculture, and the Platte River's extraordinary wetland complex creates near-ideal conditions for Culex tarsalis. Douglas County (Omaha) and Lancaster County (Lincoln) typically record the highest case totals, but the risk extends statewide.

Omaha / Eastern Nebraska
Omaha · Bellevue · Lincoln
Platte River Valley / Central NE
Grand Island · Kearney · Columbus
Very Low Low Moderate High Very High taller = more active · color = severity
Top 5
nationally for West Nile Virus cases most years
~40
mosquito species recorded in Nebraska
May–Oct
active season in eastern Nebraska
93
counties — eastern corridor carries highest WNV risk

Omaha and eastern Nebraska: the WNV hotspot

The Omaha metro — Douglas, Sarpy, and Washington counties — leads Nebraska in West Nile Virus activity most years. The Missouri River floodplain, the Papillion Creek watershed, and urban storm drain systems support large Culex tarsalis and Culex pipiens populations. Sarpy County (Bellevue) has historically been one of the most WNV-active counties in the entire United States.

The Platte River valley: the breeding corridor

The Platte River and its tributaries form a 300-mile breeding corridor from Wyoming to the Missouri River. The braided river channels, sandbars, and adjacent wet meadows provide exceptional Culex tarsalis habitat through July and August. Grand Island and Kearney sit in the most active zone, and both cities have experienced significant WNV transmission in active years.

Western Nebraska: panhandle and sandhills

The Nebraska Sandhills — the largest sand dune formation in the Western Hemisphere — support a surprising variety of wetland habitat in their interdunal lakes and marshes. Culex tarsalis is active here, and the panhandle communities (Scottsbluff, North Platte) see a compressed but real season from late June through August. WNV is detected in the panhandle most years.

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

The species that makes Nebraska a national WNV leader. Culex tarsalis thrives in the Platte River's braided channel system — the warm, shallow, sandbars-and-slough topography is textbook tarsalis habitat. During July and August, the 300-mile Platte corridor functions as a continuous breeding engine from Wyoming to the Missouri River. In high-transmission years like 2003 and 2012, Nebraska recorded some of the highest per-capita WNV rates in the nation — a direct product of this species' productivity in the central Platte valley.

Aedes vexans mosquito photograph
Aedes vexans
Floodwater Mosquito

Nebraska's most visible mosquito — the one that drives residents inside after a wet spring. Aedes vexans populations in the Missouri and Platte River floodplains can increase by orders of magnitude within a week of significant flooding. The species' eggs can remain viable in soil for years, waiting for the right flood event. Grand Island and the central Platte communities regularly experience the most intense floodwater surges in early summer, as the river peaks with Rocky Mountain snowmelt before the dry-down begins.

Culex pipiens mosquito photograph
Culex pipiens
Northern House Mosquito

The WNV vector that operates inside Omaha and Lincoln while Culex tarsalis works the surrounding farmland. Culex pipiens breeds in the urban storm drain systems, retention ponds, and residential containers that accumulate in Nebraska's two major cities. Douglas County (Omaha) consistently records the state's highest absolute WNV case totals, a product of pipiens density in the metro combined with tarsalis pressure from the agricultural belt immediately surrounding the city.

IV. Nebraska Cities at a Glance
CityPeak SeasonOff-SeasonNotes
Omaha May – Oct Off Nov–Apr Missouri River; Douglas County WNV active most years; metro spray program Check live
Lincoln May – Oct Off Nov–Apr Salt Creek corridor; Lancaster County consistently WNV-positive; active urban program Check live
Bellevue May – Oct Off Nov–Apr Sarpy County; historically one of highest WNV counties in the US; Missouri floodplain Check live
Grand Island May – Sep Off Oct–Apr Platte River corridor; center of WNV transmission in central Nebraska Check live
Kearney May – Sep Off Oct–Apr Platte River; Rainwater Basin wetlands nearby; above-average WNV pressure 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 Kansas Great Plains WNV corridor — Wichita and Kansas City see peak pressure July–August; floodwater species surge after storms 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 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 →