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Richmond Mosquito Forecast

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

Bite Index · Sunday, November 8

Moderate

Moderate mosquito activity in Richmond today: expect some bites at dusk.

Some bites at dusk and dawn, mostly near creeks, gardens and shade.

Worse than a typical November in Richmond City (usually around 0).

  • 0.9 in. of rain Oct 14–Oct 28 is now producing adults (cool weather slowed the hatch, so the window is longer than usual).
  • Tonight: a cool 50°F evening, light wind — poor flying weather, so fewer bites than the population alone would suggest.
  • At a two-week average of 57°F, larvae develop slowly and numbers are easing.

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
    22Mod.63°/38°dry
  2. Mon
    20Low64°/42°dry
  3. Tue
    26Mod.70°/40°dry
  4. Wed
    26Mod.68°/53°dry
  5. Thu
    21Mod.62°/53°0.1 in
  6. Fri
    11Low57°/44°0.1 in
  7. Sat
    11Low53°/42°dry

Protect tonight

Worth repellent if you'll be outside at dusk or dawn.

  1. A botanical or 10% picaridin lotion covers a patio evening; reapply after about two hours.
  2. A fan on the patio does real work: mosquitoes are weak fliers and avoid moving air.
Which repellent, and how much: DEET vs picaridinBest natural repellents

Why Richmond's mosquitoes do what they do

Richmond straddles the fall line of the James River, where the Piedmont meets the coastal plain, and its summers are hot and humid enough for a full Culex season. The Richmond and Henrico Health Districts trap and test; in September 2025 they alerted the public to an increased risk of West Nile transmission in Henrico.

  • The James and its creeks: river islands, Reedy Creek and the canal system leave standing water after storms.
  • Humid summers: July and August dusk conditions are ideal for flight.
  • Asian tiger mosquito: the daytime biter dominates the Fan and Church Hill's shaded yards.
  • Real winter: frosts from late October end the season.

A typical year in Richmond City

The long-run mosquito index by month from our season map (NOAA climate normals plus effort-corrected sightings). Today's Bite Index is the live version of this; the month you're in is marked.

  1. JJanuary: 0
  2. FFebruary: 0
  3. MMarch: 0
  4. AApril: 24
  5. MMay: 50
  6. JJune: 76
  7. JJuly: 94
  8. AAugust: 96
  9. SSeptember: 83
  10. OOctober: 51
  11. NNovember: 0
  12. DDecember: 0

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Richmond City'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. Four weather factors are combined on a 0–100 scale, then scaled by the season. Every factor and today's value for it is listed here so you can check the number yourself. It uses the same temperature curve and rain logic as our county-level mosquito season map, which has been validated against effort-corrected sighting data across 41 states.

BBreeding pressure

Rain 7–14 days ago (0.9 in. between Oct 14 and Oct 28). Eggs need water to hatch, and at summer temperatures the egg-to-biting-adult cycle takes about a week, so today's mosquitoes are last week's rain. Cool weather stretches the window; hot dry days shrink it as shallow water evaporates.

Weight 40%
Today 56%

DDevelopment

The trailing two-week average temperature, on the same curve as our national season map: nothing below 50°F, full speed at 78–88°F, a small penalty in extreme heat.

Weight 25%
Today 25%

ATonight's activity

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.

Weight 25%
Today 0%

GGround truth

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

Weight 10%
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.

Weight ×
Today 60%

index = 100 × S × (0.40 × (0.2 + 0.8·B) + 0.25 × D + 0.25 × A + 0.10 × (0.5 + 0.5·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 Richmond

When is mosquito season in Richmond?
May through October, peaking from July through September. Frost, usually late October or November, ends it.
Why are mosquitoes bad along the James River?
The river's islands and side channels leave pools as water levels drop after storms, and the shaded parks hold humidity at dusk. Belle Isle and the Pony Pasture run above the citywide index.
Is West Nile virus a risk in Richmond?
Yes. The health districts issued an elevated-risk alert for Henrico in 2025 and detect the virus in mosquitoes most summers. Their advisories are authoritative; follow them over the index.
Where does this forecast's data come from?
Open-Meteo weather for downtown Richmond, scored by our documented model and compared with the city's season-map climatology. Not a trap count.

Also covers Henrico, Chesterfield, Short Pump, Midlothian, Mechanicsville, Glen Allen, Belle Isle, Maymont: the forecast point is central Richmond, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 1:38 PM local time.

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