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Oklahoma · Mosquito Season Guide

Is it mosquito season in Oklahoma?

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II. Oklahoma Mosquito Season Month by month

Oklahoma sits at a climatic crossroads — Gulf Coast humidity pushing north meets Great Plains drought cycles pushing south — and the mosquito season reflects that volatility. In wet years, the Arkansas and Canadian River floodplains produce extraordinary breeding events. In dry years, Culex tarsalis and quinquefasciatus concentrate around permanent water, amplifying West Nile Virus transmission. Tulsa's Green Country is the most consistently active part of the state.

Oklahoma City / Central OK
OKC · Norman · Edmond
Tulsa / Green Country
Tulsa · Broken Arrow · Muskogee
Very Low Low Moderate High Very High taller = more active · color = severity
~60
mosquito species recorded in Oklahoma
Apr–Oct
active season statewide
WNV
detected in OKC and Tulsa metros most years
77
counties — all with seasonal exposure

Tulsa and northeastern Oklahoma: Green Country

Tulsa and the surrounding Green Country region — Rogers, Wagoner, Mayes, and Muskogee counties — is Oklahoma's most consistently mosquito-active zone. The Arkansas River, Grand Lake o' the Cherokees, and the region's extensive woodland wetlands sustain Culex quinquefasciatus and Aedes vexans populations from April through October. Tulsa County records the state's highest annual WNV case totals in most years.

Oklahoma City metro: Canadian River corridor

The Oklahoma City metro — Oklahoma, Cleveland, and Canadian counties — experiences strong Culex quinquefasciatus pressure in urban areas and Culex tarsalis in the surrounding agricultural zones. The North Canadian River and its suburban impoundments provide consistent warm-water breeding habitat. OKC runs an active nighttime spray program during peak WNV transmission season.

Southern Oklahoma: the Red River boundary

The Red River counties bordering Texas — Marshall, Bryan, Choctaw, McCurtain — see some of the state's longest seasons, starting in March and extending into November in warm years. The Ouachita Mountains of southeastern Oklahoma add forested wetland pressure, and this corner of the state has historically been active for St. Louis encephalitis in addition to WNV.

III. Oklahoma's Key Mosquito Species
Culex quinquefasciatus mosquito photograph
Culex quinquefasciatus
Southern House Mosquito

Oklahoma City and Tulsa both sit in the WNV sweet spot: warm enough for fast larval development, wet enough for standing water to persist through summer. Culex quinquefasciatus colonizes the urban storm drain network and any stagnant warm water — irrigation runoff behind strip malls, neglected pools, clogged gutters in older neighborhoods. A dusk-to-dawn biter that rarely disperses far, it drives nearly all WNV transmission in both metro areas.

Aedes albopictus mosquito photograph
Aedes albopictus
Asian Tiger Mosquito

The tiger mosquito arrived in Oklahoma in the 1990s and has since pushed well beyond the humid east into drier central Oklahoma — one of the westernmost inland populations in the country. It breeds in any container holding a few ounces of fresh water and bites aggressively during daylight. In OKC and Tulsa neighborhoods with dense tree canopy and container habitat, it often generates more resident complaints than the nighttime Culex pressure.

Aedes vexans mosquito photograph
Aedes vexans
Floodwater Mosquito

When the Arkansas, Canadian, or Red River overtops its banks — as each does regularly during wet Oklahoma springs — Ae. vexans hatches in mass emergence events that produce some of the most intense rural biting pressure in the mid-South. In flood years, populations spike so rapidly that outdoor activity becomes nearly impossible in affected counties for 7–10 days. The species isn't a significant WNV vector, but its sheer numbers make it the most visible mosquito in the state after a major weather event.

IV. Oklahoma Cities at a Glance
CityPeak SeasonOff-SeasonNotes
Oklahoma City Apr – Oct Off Nov–Mar Canadian River; urban Culex quinquefasciatus; OKC spray program active; WNV most years Check live
Tulsa Apr – Oct Off Nov–Mar Arkansas River; highest WNV totals in state; Green Country wetland complex Check live
Norman Apr – Oct Off Nov–Mar Cleveland County; Little River corridor; part of OKC metro pattern Check live
Broken Arrow Apr – Oct Off Nov–Mar Tulsa metro; Bird Creek corridor; above-average suburban pressure Check live
Edmond Apr – Oct Off Nov–Mar Oklahoma County; urban north OKC; storm drain breeding; WNV active 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 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 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 →