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Kentucky · Mosquito Season Guide

Is it mosquito season in Kentucky?

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II. Kentucky Mosquito Season Month by month

Kentucky's mosquito season is shaped by two forces: the Ohio River corridor in the north, which runs one of the longest and most intense seasons in the Upper South, and the Appalachian woodland wetlands in the east, which harbor Eastern Equine Encephalitis vectors in isolated swamp complexes. Aedes albopictus — the Asian tiger mosquito — has colonized all 120 counties and turned daytime outdoor activities into biting season from May through October.

Louisville / Ohio River Valley
Louisville · Jeffersonville · Owensboro
Lexington / Central Bluegrass
Lexington · Frankfort · Richmond
Very Low Low Moderate High Very High taller = more active · color = severity
~60
mosquito species recorded in Kentucky
Apr–Oct
active season in the Ohio River valley
120
counties — all with Ae. albopictus established
WNV
detected annually in Jefferson and Fayette counties

Louisville and the Ohio River valley

Louisville sits at the bend of the Ohio River with extensive floodplain habitat on both the Kentucky and Indiana shores. Jefferson County experiences intense pressure from the Falls of the Ohio area through the Beargrass Creek watershed. The season starts in April during warm years and runs through October — one of the longest effective windows in the Midwest. West Nile Virus is detected in Jefferson County virtually every summer.

The Bluegrass region: horse country

The Lexington metropolitan area and the surrounding Bluegrass — Fayette, Scott, Bourbon, and Clark counties — experience a classic Upper South season from May through September. The region's horse farms and their water features, along with the Kentucky River tributaries, sustain active Culex and Aedes populations. EEE has been detected in the Bluegrass in some years.

Eastern Kentucky: Appalachian woodland mosquitoes

The Daniel Boone National Forest and the Appalachian coalfield counties of eastern Kentucky see intense woodland mosquito pressure in June and July, driven by Aedes vexans and Aedes canadensis in forested wetlands. Population density is low, but outdoor workers and recreationists face consistent pressure through the summer months.

III. Kentucky's Key Mosquito Species
Culex pipiens mosquito photograph
Culex pipiens
Northern House Mosquito

The Ohio River corridor is one of the densest Culex pipiens zones in the mid-South, and Louisville sits at its center. Pipiens colonizes urban drainage infrastructure — storm drains, catch basins, and the standing water that pools in low-lying neighborhoods after summer rains — and moves WNV between corvids and humans through July and August. A late-evening biter that stays close to its breeding water, high trap counts cluster near the river bottoms and older urban neighborhoods with aging drainage.

Aedes albopictus mosquito photograph
Aedes albopictus
Asian Tiger Mosquito

Established in all 120 Kentucky counties, the tiger mosquito is the most commonly encountered species in residential areas statewide. A daytime container breeder that thrives in shaded suburban yards, it extends biting pressure from May through October — far outlasting the Culex nighttime window. It is responsible for most of the backyard biting pressure that drives Kentuckians indoors on otherwise pleasant evenings.

Aedes vexans mosquito photograph
Aedes vexans
Floodwater Mosquito

When the Ohio River rises in spring, and when summer thunderstorms flood the Wabash and Kentucky River bottomlands, Ae. vexans emerges in numbers that overwhelm any other species present. Western Kentucky's floodplain agriculture — corn and soybean fields that hold water in low spots — provides persistent larval habitat well into summer. Vexans is a strong flier; populations that hatch in river bottoms show up in Louisville neighborhoods miles away within days.

IV. Kentucky Cities at a Glance
CityPeak SeasonOff-SeasonNotes
Louisville Apr – Oct Off Nov–Mar Ohio River floodplain; Jefferson County WNV active most years; longest season in state Check live
Lexington May – Oct Off Nov–Apr Kentucky River tributaries; Bluegrass horse farm water features; EEE detected some years Check live
Bowling Green Apr – Oct Off Nov–Mar Barren River corridor; similar to Louisville pattern but lower WNV pressure Check live
Owensboro Apr – Oct Off Nov–Mar Ohio River; western KY; intense spring floodwater surges; Ae. albopictus active Check live
Covington Apr – Oct Off Nov–Mar Northern KY; part of Cincinnati metro; Ohio River; similar pressure to Louisville 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 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 →