Today's Mosquito Risk in Idaho: Real-Time Forecast & Activity Map
Check your ZIP code for local mosquito activity, West Nile risk, and prevention insights.
Built from CDC and NOAA data
Mosquito Surveillance Insights
- Annual WNV Cases
- about 15 to 30 confirmed cases annually
- Based on CDC ArboNET surveillance data
- Risk Tier
- Tier 4: Low
- Snake River irrigation feeds Cx. tarsalis populations; northern panhandle stays cooler and lower-risk.
- Per mosquito-risk-model regional tier
- Highest-Risk Areas
- Ada, Canyon, Bonneville, Twin Falls (metros and Snake River Plain Cx. tarsalis)
Current Situation in Idaho
Idaho carries a low to moderate WNV burden of roughly 15 to 30 confirmed human cases annually, with risk concentrated across the Snake River Plain irrigated farmland from the Treasure Valley around Boise through Twin Falls and on to Idaho Falls. The Snake River irrigation grid sustains dense Cx. tarsalis populations through summer off potato, sugar beet, and alfalfa fields, and the agricultural Culex drives most of the state's WNV transmission. The forested northern panhandle around Coeur d'Alene runs cooler and wetter, with mosquito pressure dominated by floodwater Aedes off snowmelt and lakeshore wetlands rather than disease vectors. Aedes aegypti and Aedes albopictus are not established. EEE is rare. The Sawtooth Range and Bitterroot Mountains stay too cold for sustained transmission. Biting season runs June through September.
Snapshot of the current mosquito situation in Idaho, drawn from CDC ArboNET surveillance and the regional risk model.
- Risk Level
- Low
- Peak Activity
- July through September
- Dominant Vector
- Western Encephalitis Mosquito (Culex tarsalis) statewide and dominant WNV vector
Where Mosquitoes Breed in Idaho
Idaho mosquito habitat is built on the Snake River Plain irrigated farmland and the river corridors that feed it. The Snake River from Idaho Falls through Twin Falls and on across the Treasure Valley around Boise, Meridian, and Nampa holds the densest Cx. tarsalis populations in the state, with irrigation canals, flood-irrigated pastures, and tail-water ponds producing sustained summer biting. The Boise River corridor through Ada and Canyon counties carries seasonal Aedes vexans floods and steady Cx. tarsalis. The Camas Prairie in north central Idaho holds wet meadows and seasonal Aedes hatches. The Clearwater River and lower Salmon corridors hold steady summer populations off riparian wetlands. Lake Coeur d'Alene shoreline marshes and the Hells Canyon backwaters carry seasonal mosquito populations. The Sawtooth Range and Bitterroot Mountains stay cool and lower-pressure outside snowmelt Aedes pulses on the canyon trails.
Hotspot Counties & Areas
- Ada County (Boise, Meridian, Treasure Valley)
- Canyon County (Nampa, Caldwell)
- Bonneville County (Idaho Falls, upper Snake)
- Twin Falls County (Twin Falls, Magic Valley)
- Snake River Plain irrigated farmland
- Boise River corridor
- Camas Prairie (Camas County)
- Lake Coeur d'Alene shoreline (Kootenai County)
Seasonal Activity Pattern
Biting starts in early to mid June across the Snake River Plain as irrigation cycles open up, peaks late July through August, and tapers through September. WNV cases concentrate in August across the Treasure Valley and the irrigated counties of the southern plain. Cx. tarsalis populations build through July with the irrigation cycle and stay elevated through August. The northern panhandle around Coeur d'Alene runs a week or two behind the southern plain on phenology and carries lighter late-summer disease pressure. Snowmelt off the Sawtooth and Bitterroot ranges produces sharp floodwater Aedes pulses through late June. Cool nights at elevation hold high country activity down.
Monthly Biting Intensity (Mountain West)
Idaho Mosquito Risk Profile
- WNV burden level
- Low
- about 15 to 30 confirmed cases annually
- EEE risk
- Rare
- Peak biting season
- June through September
- Top urban risk areas
- Boise (Ada)
- Meridian (Ada)
- Nampa (Canyon)
- Idaho Falls (Bonneville)
Signature habitat: Snake River Plain irrigated farmland, Treasure Valley, Boise River wetlands.
Climate driver: Snake River irrigation feeds Cx. tarsalis populations; northern panhandle stays cooler and lower-risk.
Check Your Local Mosquito Risk
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Common Mosquitoes in Idaho
Understanding which mosquitoes are active in Idaho helps you identify threats and take appropriate precautions. Click any card for details.
Northern House Mosquito
Culex pipiens
Risk: West Nile virus, St. Louis encephalitis, dog heartworm.
Key feature: Medium brown body with banded abdomen. Looks nearly identical to Cx. quinquefasciatus.
Active: Late spring through early fall in the north. Adult females overwinter in basements, garages, and storm drains.
West Nile Virus
Vector: Northern House Mosquito
West Nile Virus
The dominant West Nile vector across the northern half of the US. About 80% of infections are asymptomatic.
What to watch for
- Onset typically 2 to 15 days after a bite
- Most cases mild or asymptomatic, small fraction severe
- Neurological signs (severe headache, neck stiffness, confusion) need ER care
Breaking the Cycle in Idaho
The mosquito lifecycle takes about a week. These habits cut local biting pressure faster than anything else, building multiple layers of protection.
Drain the Yard Weekly
Empty buckets, planter saucers, kiddie pools, tarps, and clogged gutters. A week of standing water is one full mosquito generation.
Repel Before Going Out
EPA-registered DEET (20-30%), picaridin (20%), IR3535, or oil of lemon eucalyptus. Apply before going outside, especially at dusk and dawn.
Seal the House
Window and door screens with no tears. AC and porch fans both work. Mosquitoes struggle to fly upwind even at 1-2 mph air speed.
Treat Outdoor Clothing
Permethrin-treated long sleeves and pants for evening yard work, hiking, or fishing. Remains effective through 70+ wash cycles.
If You Develop Symptoms
Most mosquito bites are harmless. A small fraction can transmit illness, and knowing the timeline matters more than panicking at every itch.Five things to know.
Watch for fever
Fever, body aches, headache, or fatigue 2 to 15 days after a bite. West Nile often feels like flu, and most infections never get diagnosed.
Note where and when
A rough record of where and when you got bitten helps your doctor decide what to test for. Date, location, mosquito-heavy areas you visited.
Get help fast for neuro signs
Severe headache, neck stiffness, confusion, vision changes, or sudden muscle weakness can mean neuroinvasive WNV or EEE. Both are medical emergencies.
Pregnant exposure?
If pregnant and bitten in an area with documented Zika or local dengue transmission, mention to your OB. Same goes for travel exposure.
Children and seniors
Higher risk of severe disease from WNV, EEE, and dengue in adults over 60 and children under 5. Early call to the pediatrician or PCP if symptoms appear.
Heading to a lake in Idaho?
Live water temperatures and swim conditions for Lake Coeur d'Alene.
See Idaho lake temperaturesWhen does mosquito season end in Idaho?
Mosquito activity winds down after the first hard freeze, which in Idaho typically arrives around Sep 28. See the local first-frost window and city-by-city freeze dates.
Idaho first frost datesAlso worried about ticks in Idaho?
Lyme disease risk and tick activity track different seasonal patterns than mosquitoes. See your Idaho tick forecast.
View Idaho tick forecastStay Safe in Idaho
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