The four layers
A single diurnal number would misfit mosquitoes, because the daytime biters and the dusk-to-night disease carriers behave nothing alike. So the score is built in four layers: how favorable today's weather is for biting, how large the local population is right now, which species are driving it, and a separate West Nile and EEE disease overlay. The first four signals set the everyday bite-risk number; the fifth sits on top.
- 1
Today's weather for bitingOpen-Meteo
Mosquito biting peaks around 79°F and shuts down below about 50°F and above the mid-90s, so temperature is a curved gate, not a simple threshold. Wind matters too: even a light breeze thins the scent plume mosquitoes home in on, and a stiff wind grounds them. Humid air helps them survive and hunt. We read each town's temperature, wind, and humidity every day; this gate is often what makes two nearby towns, or two days, feel different.
- 2
The season and recent rainSeasonal calendars + Open-Meteo
Populations build from about mid-June, peak in mid-to-late summer, and fade with the first cool nights, and each species rides its own curve. Rain is the other lever: the dominant summer nuisance biter breeds in ground pools left by heavy rain, so its numbers surge roughly a week after a soaking and stay high for about two weeks. We fold the season and the last week's rainfall into how big the local population is today.
- 3
Local breeding habitatESA WorldCover
Mosquitoes breed in standing water, so from 10-meter satellite land cover we measure each town's wetland and marsh, open water, and developed cover. Marshes and floodplains breed the floodwater and cattail mosquitoes; developed areas breed the house mosquito in storm-drain catch basins and backyard containers. This is the part of the score that is truly local to your town, and it is what separates a marshy town from a dry one in the same county.
- 4
Which mosquitoes are bitingVector ecology
Five species drive risk here, and they bite at different times: the floodwater and Asian tiger mosquitoes are the daytime and dawn/dusk nuisance biters; the house mosquito (West Nile) bites dusk into the night; the swamp and cattail-marsh mosquitoes (EEE) bite after sunset. Each town page shows which species dominate its score. Because there is no per-county mosquito surveillance to draw on, that prominence is modeled from habitat, season, and weather, not counted in the field.
- 5
West Nile and EEE overlayVector ecology (surveillance pending)
Transmission is not the same as biting, so disease risk is a separate layer. West Nile risk tracks the house mosquito in developed areas and peaks in late-summer heat (its transmission optimum, near 76°F, is a touch cooler than the biting optimum). EEE risk tracks the swamp and cattail-marsh mosquitoes and climbs after mid-July, when the cycle shifts from birds toward mammals. Today these levels are modeled from habitat and season; live ArboNET and state-health-department surveillance is planned to sharpen them.
How they combine
The everyday score is nuisance biting: each species contributes from its season, the recent-rain brood, its habitat in the town, and how much it bites people, all suppressed by the shared weather gate. A cool, windy, or dry day pulls the whole number down no matter how much habitat a town has. Those contributions are summed and scaled to 0 to 100, with a curve that keeps the driest towns genuinely low and reserves the red band for real hotspots. The West Nile and EEE overlay then adds a bounded lift where habitat and season favor transmission.
Every town page shows the split, so you can see how much of the day's number is each species, and that the species mix and disease levels are modeled rather than surveilled.
Limits and caveats
This is a defensible heuristic, not a validated epidemiological model. It estimates how favorable conditions are for mosquito activity in a place on a given day; it cannot tell you whether a specific mosquito carries disease. Land cover reflects a town's broad make-up, not your yard, and species prominence and the West Nile / EEE levels are modeled from habitat and season rather than measured from trapping or positive-pool surveillance.
What counts as a town. We score every U.S. Census place and county subdivision in our footprint, more than 25,000 towns and cities across 38 states. Uninhabited fragments are excluded, and a municipality that straddles a county line is scored once per county piece. We say "towns" throughout the site as shorthand for all of these.
Not medical advice. If you develop a fever, headache, or other symptoms after mosquito bites, contact a healthcare professional and see CDC mosquito guidance.