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II · Season Timing

Typical season — Raleigh

Activity varies significantly by region — coastal plain starts 3–4 weeks before the mountains

Coastal Plain

Wilmington · New Bern · Outer Banks

Piedmont

Raleigh · Charlotte · Greensboro

Mountains

Asheville · Boone · La Crosse hotspot

Minimal Low Moderate High Peak taller = more active · color = severity

Choose a city

60+

mosquito species recorded in North Carolina

Apr–Oct

active season — coastal plain starts earlier

June–Aug

peak pressure months statewide

WNV + LAC

WNV statewide; La Crosse encephalitis in mountains

IV · Key Species

Culex quinquefasciatus

⚠ WNV Vector — Primary Risk

The Southern house mosquito — dominant Culex species across the NC Piedmont and coastal plain. Breeds in warm, organically enriched standing water: neglected containers, stormwater infrastructure, ornamental ponds. Bites dusk through dawn. Primary West Nile vector in urban and suburban NC; NCDPH WNV surveillance runs May–October.

Aedes albopictus

Asian Tiger Mosquito

Established in all 100 North Carolina counties — among the most complete state-level colonizations in the US. Aggressive daytime biter, most active in shaded suburban yards April through October. Breeds in any small container holding water. Particularly dense in the Triangle (Raleigh-Durham-Chapel Hill) and Charlotte metro. Most biting activity in early morning and late afternoon.

Aedes vexans

Inland Floodwater Mosquito

A significant nuisance species across NC's river corridors — Cape Fear, Neuse, and Catawba river floodplains all produce intense populations after heavy rains. Not a primary disease vector but responsible for the aggressive biting that spikes after storms. In the western mountains, Aedes triseriatus (tree-hole mosquito) is the La Crosse encephalitis vector — its populations are far less visible than floodwater species.

V · North Carolina Mosquito Context

Three ecosystems, three different seasons

North Carolina spans three distinct ecological regions that produce very different mosquito seasons. The coastal plain — from Wilmington inland to Fayetteville and Greenville — runs one of the longest seasons in the Southeast: March through November, with intense pressure from June through September. The Piedmont plateau (Raleigh, Charlotte, Greensboro) sees a compressed April–October season with peak pressure in July and August. The western mountain counties run a shorter, cooler season from May into September — but they carry a disease risk unique in the eastern US.

La Crosse encephalitis: the mountain risk most people don't know about

North Carolina consistently reports more La Crosse encephalitis (LAC) cases than any other state — sometimes accounting for more than half of the nation's annual total. LAC is transmitted by Aedes triseriatus, a tree-hole mosquito that breeds in hardwood forest hollows in the Appalachian foothills. Unlike WNV, LAC primarily affects children under 16 and can cause severe neurological illness. The highest-risk counties are in western NC: Buncombe, Henderson, Madison, McDowell, and Transylvania. NCDPH issues LAC advisories for the western region through the summer. Check NCDHHS arboviral reports →

Asian tiger mosquitoes in all 100 counties

North Carolina completed one of the most thorough Ae. albopictus colonizations of any state east of the Mississippi. Every county now has established populations. Unlike the night-biting Culex species, tiger mosquitoes bite actively during daylight — which catches most people off-guard. Removal of standing water in containers remains the single highest-leverage action: tires, bird baths, clogged gutters, and ornamental pot saucers each support independent breeding populations.

VI · City-by-City Breakdown

City	Season	Off-season	Notes	Live data
Raleigh	Apr – Oct	Off Nov–Mar	Triangle metro; Ae. albopictus dominant in residential areas; Jordan Lake and Falls Lake watershed corridors; Cx. quinquefasciatus active in urban stormwater infrastructure; WNV detections in Wake County surveillance traps most seasons; urban heat extends season at both ends; significant pressure in wooded suburban neighborhoods	Check live
Charlotte	Apr – Oct	Off Nov–Mar	Rapidly expanding metro with Ae. albopictus in every suburban neighborhood; Catawba River wetlands amplify populations; WNV detected in Mecklenburg County; urban density and heat island effect extend the effective season; Lake Norman shoreline creates additional breeding habitat; one of the highest Ae. albopictus complaint volumes in the state	Check live
Greensboro	Apr – Oct	Off Nov–Mar	Triad metro; Ae. albopictus well established across residential areas; Lake Brandt and Horsepen Creek watershed; Cx. quinquefasciatus present in urban areas; WNV detected in Guilford County; lower peak pressure than coastal plain but significant daytime biting from tiger mosquitoes throughout summer	Check live
Durham	Apr – Oct	Off Nov–Mar	Duke Forest and Eno River State Park provide extensive wooded habitat; Ae. albopictus dense in tree-canopy neighborhoods; Durham County WNV surveillance positive most seasons; Ae. triseriatus (La Crosse vector) present in hardwood hollows near the Piedmont/mountains transition; university campus grounds with high container-breeding pressure	Check live
Fayetteville	Mar – Oct	Off Nov–Feb	Coastal plain location — extended season with March starts common; Cape Fear River floodplain drives intense Ae. vexans surges after storm events; Ae. albopictus dominant in residential areas; Fort Bragg (now Fort Liberty) area; WNV present in Cumberland County; consistently among the earliest-starting cities in NC; significant military installation vector control programs	Check live
Wilmington	Mar – Nov	Off Dec–Feb	Cape Fear River estuary and extensive coastal wetlands; one of the longest and most intense mosquito seasons in NC; salt marsh and freshwater species both active; Ae. albopictus and Cx. quinquefasciatus dominant; New Hanover County among the highest mosquito complaint volumes in the state; coastal warmth extends activity well into fall; aggressive biting from March through November	Check live
Asheville	May – Sep	Off Oct–Apr	Western mountain location — shorter, cooler season (3–4 weeks shorter than piedmont); lower overall density; La Crosse encephalitis risk from Ae. triseriatus in surrounding hardwood forests; Buncombe County within the highest LAC-risk region in the state; elevation suppresses peak but not elimination; French Broad River corridor; Ae. albopictus present but less dense than lower elevations	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 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 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 →