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Norfolk Mosquito Forecast

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

Bite Index · Sunday, November 8

Moderate

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

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

About normal for November in Norfolk City.

  • 1.0 in. of rain Oct 16–Oct 29 is now producing adults (cool weather slowed the hatch, so the window is longer than usual).
  • Tonight: a cool 48°F evening, light wind — poor flying weather, so fewer bites than the population alone would suggest.
  • At a two-week average of 60°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
    26Mod.58°/42°dry
  2. Mon
    26Mod.63°/43°dry
  3. Tue
    32Mod.70°/44°dry
  4. Wed
    31Mod.68°/57°dry
  5. Thu
    32Mod.70°/55°dry
  6. Fri
    17Low61°/46°dry
  7. Sat
    20Low51°/43°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 Norfolk's mosquitoes do what they do

Norfolk is a low city of tidal creeks and rivers at the mouth of the Chesapeake, and the salt marsh around Hampton Roads produces mosquitoes the way the Gulf Coast does. The Norfolk Health Department's Mosquito Control program traps across the city and publishes its counts and West Nile and EEE test results as open data, which this page reads directly.

  • Tidal salt marsh: the Elizabeth and Lafayette Rivers and the Back Bay marshes produce salt-marsh Aedes broods after spring tides and storms.
  • Flooding: nuisance tidal flooding leaves standing water in streets and yards across the city.
  • Humid summers: July and August dusk conditions are ideal for flight.
  • Real winter: frosts from November end the season.

A typical year in Norfolk 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: 26
  5. MMay: 50
  6. JJune: 76
  7. JJuly: 94
  8. AAugust: 98
  9. SSeptember: 87
  10. OOctober: 59
  11. NNovember: 23
  12. DDecember: 0

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Norfolk 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 (1.1 in. between Oct 16 and Oct 29). 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 65%

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 37%

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 Norfolk 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 Norfolk

When is mosquito season in Norfolk?
May through October, peaking from July through September. Salt-marsh broods can come earlier after big spring tides; frost ends the season.
Why are the mosquitoes so bad in Ocean View and along the rivers?
Salt-marsh mosquitoes hatch in huge numbers when tides or storms flood the marsh, and they fly miles. The shoreline neighborhoods run well above the citywide index.
Is West Nile virus a risk in Norfolk?
Yes. The city detects West Nile in mosquito samples most summers and tests sentinel chickens for EEE. Its results are read into this page; the Health Department's own advisories are authoritative.
Where does this forecast's data come from?
Open-Meteo weather for downtown Norfolk and the city's own trap counts from data.norfolk.gov, scored by our documented model. The trap counts are a real measurement and the strongest input to the ground-truth factor.

Also covers Virginia Beach, Chesapeake, Portsmouth, Hampton, Newport News, Suffolk, Ocean View, the Elizabeth River Trail: the forecast point is central Norfolk, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 12:28 PM local time.

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