Mosquito forecast
Houston Mosquito Forecast
Today's mosquito activity in Houston, the week ahead, and what to do about it. Updated hourly.Today's mosquito activity in Houston on a 0–100 Bite Index, the week ahead, and what to do about it. Built from the rain and temperature that drive Harris County's trap counts; updated hourly.
Bite Index · Sunday, November 8
High
High mosquito activity in Houston today and easing through the week. Cover up or use repellent after 6 pm.
Bites within a few minutes outdoors at dusk. Repellent or long sleeves pay off.
About normal for November in Harris County.
- Only 0.2 in. of rain Oct 22–Oct 31, so few new breeding sites; what's biting is coming from irrigation, pools and creeks.
- Tonight: a cool 65°F evening, light wind — good flying weather for mosquitoes.
- A two-week average of 71°F keeps populations growing, just more slowly than midsummer.
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.
- Today56HighHigh70°/60°dry
- Mon50HighHigh66°/59°0.2 in
- Tue56HighHigh70°/59°dry
- Wed56HighHigh78°/66°dry
- Thu43HighHigh79°/65°dry
- Fri38Mod.Moderate66°/56°dry
- Sat45HighHigh70°/53°dry
Protect tonight
Use repellent for any time outside after about 6 pm.
- 20% picaridin or 20–30% DEET for the evening; follow the label's reapplication window.
- Long sleeves and pants in light colors cut bites roughly in half on their own.
- Skip the yard work at dusk: the hour around sunset is the heaviest biting of the day.
Why Houston's mosquitoes do what they do
Houston is flat, humid and fifty feet above sea level, with bayous threading every neighborhood, so water that falls stays. Harris County Public Health runs one of the largest mosquito-control operations in the United States, trapping across hundreds of sites each week and testing for West Nile, St. Louis encephalitis and the Aedes-borne viruses; the county logged 520 positive samples and seven human West Nile cases in 2024 alone.
- Bayous and ditches: Buffalo, Brays, White Oak and Sims Bayous and the roadside ditch network hold water for days after any rain.
- Humidity: Gulf air keeps dusk humidity above 70% most of the year, ideal for flight and egg survival.
- Twelve-month season: Harris County never drops to asleep; mosquitoes are active in a mild January.
- Aedes aegypti is established: the dengue and Zika vector breeds in containers across the city, not just in wetlands.
A typical year in Harris County
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.
- JJanuary: 27
- FFebruary: 27
- MMarch: 40
- AApril: 61
- MMay: 87
- JJune: 100
- JJuly: 95
- AAugust: 88
- SSeptember: 92
- OOctober: 81
- NNovember: 61
- DDecember: 42
Local surveillance and West Nile virus
The Bite Index measures nuisance biting, not disease. Harris 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.
- Harris County Public Health — Mosquito & Vector Control Division
One of the largest mosquito-control programs in the country: hundreds of traps a week, species identification, virus testing, and spray operations by ZIP.
- Texas DSHS — Arbovirus surveillance
Statewide weekly West Nile, dengue and other mosquito-borne disease reports.
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 (0.2 in. between Oct 22 and Oct 31). 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.
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.
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.
GGround truth
A nudge from local trap counts and reports when we have them. For Houston this is neutral today; the health department's surveillance is linked above and will feed this factor as we wire it in.
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.
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 Houston
- When is mosquito season in Houston?
- Effectively year-round. Harris County traps mosquitoes every month; activity peaks from May through October and dips, but rarely stops, in December and January. The Bite Index reflects that: a warm wet week in winter still scores.
- Why are mosquitoes so bad after it rains in Houston?
- Houston's drainage is slow by design, so rain sits in ditches, bayou margins and yards. At Gulf Coast temperatures eggs become biting adults in about a week, which is why the worst nights come 7 to 14 days after a storm, not during it.
- Is West Nile virus a risk in Houston?
- Yes. Harris County records positive mosquito samples every summer, often in the hundreds, and human cases most years. HCPH posts positive sample locations and spray schedules; when your ZIP is listed, treat dusk and dawn as high-risk hours regardless of the index.
- Where does this forecast's data come from?
- Weather from Open-Meteo for central Houston; the scoring is ours and is documented below. It is a model of conditions, not a trap count. Harris County's surveillance is linked above and is the authoritative source for disease risk.
Also covers Katy, Sugar Land, The Woodlands, Pearland, Pasadena, Baytown, Memorial Park, Buffalo Bayou: the forecast point is central Houston, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 12:38 PM local time.