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Brownsville Mosquito Forecast

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

Bite Index · Sunday, November 8

Moderate

Moderate mosquito activity in Brownsville today and climbing toward severe by Nov 14: expect some bites at dusk.

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

Quieter than a typical November in Cameron County (usually around 53).

  • Only 0.0 in. of rain Oct 25–Nov 1, so few new breeding sites; what's biting is coming from irrigation, pools and creeks.
  • Two weeks averaging 78°F is ideal breeding weather: egg to biting adult in about a week.
  • Tonight: a 72°F evening, light wind — good flying weather for mosquitoes.

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
    35Mod.78°/72°3.0 in
  2. Mon
    34Mod.73°/71°0.5 in
  3. Tue
    34Mod.82°/71°0.1 in
  4. Wed
    34Mod.81°/72°dry
  5. Thu
    34Mod.78°/70°dry
  6. Fri
    33Mod.75°/64°dry
  7. Sat
    91Severe76°/62°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 Brownsville's mosquitoes do what they do

Brownsville is the southern tip of Texas, where the Rio Grande meets the Gulf in resacas, palm groves and salt flats, and it is the one US metro where dengue is a recurring local story. Cameron County Public Health traps and sprays across the county and recorded locally acquired dengue in 2024 alongside its usual West Nile detections.

  • Resacas: the old river channels that wind through the city are permanent breeding habitat.
  • Aedes aegypti: the dengue vector is abundant in the dense neighborhoods on both sides of the border.
  • Salt flats and the Laguna Madre: salt-marsh broods after tropical rain and high tides.
  • No winter: Cameron County's season gate is open from March to December.

A typical year in Cameron County

What the Bite Index typically reads here each month, from Cameron 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: 11
  2. FFebruary: 14
  3. MMarch: 28
  4. AApril: 42
  5. MMay: 74
  6. JJune: 86
  7. JJuly: 72
  8. AAugust: 70
  9. SSeptember: 86
  10. OOctober: 85
  11. NNovember: 53
  12. DDecember: 27

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Cameron 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 (0.0 in. between Oct 25 and Nov 1), 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 0%

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 99%

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 100%

GGround truth

A nudge from local trap counts and reports when we have them. For Brownsville 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 100%

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 Brownsville

When is mosquito season in Brownsville?
All year, peaking from May through October and again after fall rains. A brief cold snap in January is the only lull.
Why does Brownsville get dengue?
Aedes aegypti is abundant, the border region sees dengue in travelers, and warm temperatures let the virus complete its cycle in the mosquito. Texas confirmed locally acquired dengue in Cameron County in 2024.
Is West Nile or dengue a risk in Brownsville?
Both are detected locally. Cameron County Public Health's advisories are authoritative; follow them over the index, which measures nuisance biting.
Where does this forecast's data come from?
Open-Meteo weather for central Brownsville, scored by our documented model and compared with Cameron County's climate normals. It does not include tide data.

Also covers Harlingen, San Benito, Los Fresnos, Port Isabel, South Padre Island, Matamoros, the Resaca de la Palma, Boca Chica: the forecast point is central Brownsville, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 4:28 PM local time.

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