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Los Angeles Mosquito Forecast

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

Bite Index · Sunday, November 8

Low

Mosquito activity in Los Angeles is low today and climbing toward high by Nov 14.

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

Worse than a typical November in Los Angeles County (usually around 4).

  • It's the edge of the season; warm weeks like this one keep it going past the calendar.
  • Tonight: a 69°F evening, light wind, dry air — average conditions for biting.
  • 0.7 in. of rain Oct 21–Oct 30 is now producing adults (cool weather slowed the hatch, so the window is longer than usual).

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
    19Low88°/57°dry
  2. Mon
    27Mod.89°/63°dry
  3. Tue
    25Mod.85°/63°dry
  4. Wed
    25Mod.85°/71°dry
  5. Thu
    35Mod.82°/70°dry
  6. Fri
    34Mod.80°/69°dry
  7. Sat
    42High78°/69°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 Los Angeles's mosquitoes do what they do

Los Angeles has a dry-summer climate and a wet-yard culture: irrigated lawns, pools, fountains and the concrete channels of the LA River give Culex all the water they need, and since the 2010s the invasive Aedes aegypti — the aggressive daytime ankle-biter — has spread through nearly every neighborhood. The Greater Los Angeles County Vector Control District traps and tests across the basin and detected West Nile by late May in 2026.

  • Aedes aegypti: the small black-and-white daytime biter is now the dominant nuisance in LA yards; it breeds in saucers, drains and anything holding a spoonful of water.
  • Irrigation and pools: with no summer rain, the city's water use is the breeding habitat.
  • River channels and spreading grounds: the LA and San Gabriel River systems breed Culex in the slow reaches.
  • Marine layer: cooler, humid nights near the coast; hotter, drier valleys inland, where the index runs higher.

A typical year in Los Angeles County

What the Bite Index typically reads here each month, from Los Angeles 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: 1
  5. MMay: 7
  6. JJune: 17
  7. JJuly: 24
  8. AAugust: 26
  9. SSeptember: 23
  10. OOctober: 15
  11. NNovember: 4
  12. DDecember: 0

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Los Angeles 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 (0.7 in. between Oct 21 and Oct 30), 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 55%

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 58%

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 50%

GGround truth

A nudge from local trap counts and reports when we have them. For Los Angeles 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 60%

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 Los Angeles

When is mosquito season in Los Angeles?
June through October, peaking from August into October, later than most of the country because LA's warmest weeks come in late summer. Aedes aegypti can bite in any warm month.
Why am I getting bitten on the ankles in the daytime?
That is Aedes aegypti, which arrived in LA County in the 2010s and now lives in most neighborhoods. It bites by day, stays low, and breeds within a few hundred feet of your house, usually in your own yard's containers. Dumping water weekly matters more than spraying.
Is West Nile virus a risk in Los Angeles?
Yes. LA County records positive samples every summer and human cases most years, concentrated in the San Fernando and San Gabriel Valleys. The district's announcements and the state's weekly table are authoritative; follow them over the index.
Where does this forecast's data come from?
Open-Meteo weather for downtown LA, scored by our documented model. The index is a basin-wide number; the inland valleys run above it and the coast below. The "typical for this month" baseline is the same model on the county's climate normals.

Also covers Long Beach, Pasadena, Glendale, Santa Monica, Burbank, the San Fernando Valley, Griffith Park, the LA River: the forecast point is central Los Angeles, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 2:28 PM local time.

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