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Lexington Mosquito Forecast

Today's mosquito activity in Lexington, the week ahead, and what to do about it. Updated hourly.

Bite Index · Sunday, November 8

Low

Mosquito activity in Lexington is low today.

Few mosquitoes. You may see one or two at dusk near water.

About normal for November in Fayette County (typically around 0).

  • Off-season: even with rain and warmth, populations are a fraction of summer's.
  • Only 0.4 in. of rain Oct 15–Oct 28, so few new breeding sites; what's biting is coming from irrigation, pools and creeks.
  • Tonight: a cool 50°F evening, light wind — poor flying weather, so fewer bites than the population alone would suggest.

The week ahead

Each day's Bite Index, from this week's weather and the rain that is still hatching. Forecast days get less certain as the week goes on.

  1. Today
    1Low60°/32°dry
  2. Mon
    1Low62°/39°dry
  3. Tue
    1Low63°/39°dry
  4. Wed
    1Low64°/42°0.1 in
  5. Thu
    0Low55°/35°0.5 in
  6. Fri
    0Low37°/33°0.2 in
  7. Sat
    0Low45°/27°dry

Protect tonight

You can probably skip repellent tonight.

  1. If you're near a creek, pond or heavy shade at dusk, a light application on ankles and arms is plenty.
  2. Good night to tip out any containers holding water; what you empty now won't hatch next week.
Which repellent, and how much: DEET vs picaridinBest natural repellents

Why Lexington's mosquitoes do what they do

Lexington's Bluegrass is rolling horse country with limestone creeks and humid summers, and the Lexington-Fayette County Health Department traps, tests and sprays by neighborhood when West Nile turns up. Kentucky issued a statewide health alert in 2025 after a rise in human cases, several of them in Lexington.

  • Limestone creeks: Town Branch, Wolf Run and the Elkhorn tributaries pool after storms.
  • Horse farms: water troughs and pond margins are breeding habitat at the city's edge.
  • Humid summers: July and August dusk conditions are ideal for flight.
  • Real winter: frosts from late October end the season.

A typical year in Fayette County

What the Bite Index typically reads here each month, from Fayette County's 30-year climate normals run through the same model as today's number. The month you're in is marked; the season map shows the same long-run picture for every county.

  1. JJanuary: 0
  2. FFebruary: 0
  3. MMarch: 0
  4. AApril: 0
  5. MMay: 19
  6. JJune: 58
  7. JJuly: 74
  8. AAugust: 75
  9. SSeptember: 60
  10. OOctober: 13
  11. NNovember: 0
  12. DDecember: 0

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Fayette County's health department traps and tests mosquitoes through the season and publishes positive West Nile pools by ZIP code. When your ZIP has an active advisory, follow it regardless of today's number.

How the Bite Index is scored

The index is a model of conditions, not a mosquito count. Warmth and water set the size of the population, tonight's weather sets how much of it flies, and the season and local reports adjust the result. Every factor and today's value for it is listed here so you can check the number yourself. Warmth and Water are exactly the climate core of our county-level mosquito season map; the map shows that core on 30-year normals for every county, and “typical for this month” is the same model run on this county's normals, so the comparison is like for like.

WWater

Rain over the egg-to-adult window (0.4 in. between Oct 15 and Oct 28), expressed as a monthly rate on the same wetness curve the season map uses. At summer temperatures eggs become biting adults in about a week, so today's mosquitoes are last week's rain. Cool weather stretches the window; hot dry days shrink it. Irrigation, creeks and pools keep a 35% floor even in a drought.

Role scales
Today 6%

TWarmth

The trailing two-week average temperature on the season map's curve: nothing below 50°F, full speed at 78–88°F, a small penalty in extreme heat. Multiplied with Water, so a cool fortnight caps the index however wet it has been.

Role gates
Today 30%

ATonight

Whether the population that exists will actually fly and bite this evening: dusk temperature (65–85°F is ideal), wind (they stop flying around 10 mph), humidity, and rain around sunset. Scales the index between half and full.

Role 0.5–1×
Today 0%

GGround truth

A nudge from local trap counts and reports when we have them. For Lexington this is neutral today; the health department's surveillance is linked above and will feed this factor as we wire it in.

Role ±15%
Today neutral

SSeason gate

A multiplier from the calendar: fully open in the city's season months, half-open in the shoulder months, nearly closed in deep winter unless the week is warm. Below a 50°F weekly average the index is simply 0.

Role ×
Today 15%

index = 100 × S × [T × (0.35 + 0.65·W)] × (0.5 + 0.5·A) × (1 + 0.15·G)

Bands: Low 0–20 · Moderate 21–40 · High 41–60 · Very High 61–80 · Severe 81–100. Weather is from Open-Meteo (observations and the 7-day forecast), refreshed hourly. The lag and temperature thresholds follow published work on Culex and Aedes development (Rueda et al. 1990; Cornell NRCC degree-day emergence; JAMCA 2024 on rainfall two to four weeks before trap peaks).

Questions people ask about mosquitoes in Lexington

When is mosquito season in Lexington?
June through September, peaking in July and August. The first frost, usually late October, ends it.
Why did Kentucky issue a West Nile alert in 2025?
Human cases rose sharply across the state, with several in Lexington, prompting the health department to spray affected neighborhoods and the state to issue an alert. Late summer is the risk window.
Is West Nile virus a risk in Lexington?
Yes. Fayette County detects it in mosquito batches most summers and recorded multiple human cases in 2025. The health department's notices are authoritative; follow them over the index.
Where does this forecast's data come from?
Open-Meteo weather for downtown Lexington, scored by our documented model and compared with Fayette County's climate normals. Not a trap count.

Also covers Nicholasville, Georgetown, Richmond, Versailles, Winchester, Frankfort, the Arboretum, Jacobson Park: the forecast point is central Lexington, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 5:28 PM local time.

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