Today's Mosquito Risk in Montana: 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 10 to 25 confirmed cases annually
- Based on CDC ArboNET surveillance data
- Risk Tier
- Tier 4: Low
- Cx. tarsalis activity tracks irrigated agriculture; western mountain valleys see far less than eastern plains.
- Per mosquito-risk-model regional tier
- Highest-Risk Areas
- Yellowstone, Cascade, Gallatin (metros); Yellowstone Valley and irrigated eastern counties (Cx. tarsalis)
Current Situation in Montana
Montana runs a low to moderate WNV burden of roughly 10 to 25 confirmed human cases annually, with risk concentrated where irrigation meets the eastern plains. The Yellowstone River corridor through Billings and the irrigated valleys east of the Continental Divide carry the bulk of Cx. tarsalis transmission, while the forested high country above timberline stays largely mosquito-free. The Bitterroot Valley and Flathead Lake basin hold steady summer populations off pasture and lakeshore wetlands. Aedes aegypti and Aedes albopictus are not established. EEE is rare. Cool nights compress the season and the state's small population masks per-capita exposure in agricultural counties. Biting season runs June through August.
Snapshot of the current mosquito situation in Montana, 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) where irrigated
Where Mosquitoes Breed in Montana
Montana mosquito habitat is built on irrigated valleys, river bottomlands, and prairie pothole wetlands east of the divide. The Yellowstone River corridor through Billings and on across the Crow Reservation produces sustained summer Cx. tarsalis off irrigated alfalfa and sugar beet fields. The Bighorn River bottoms and the Charles M. Russell National Wildlife Refuge along the Missouri carry steady summer populations. The Flathead Lake basin and the Bitterroot Valley around Missoula hold lakeshore and pasture habitat that produces moderate biting through July. Glacier National Park and the Beaverhead-Deerlodge National Forest run cool with sharp snowmelt Aedes hatches at lower elevations and clean air above timberline. The Missouri River headwaters around Three Forks hold seasonal floodwater Aedes.
Hotspot Counties & Areas
- Yellowstone County (Billings, Yellowstone River)
- Missoula County (Missoula, Bitterroot confluence)
- Cascade County (Great Falls, Missouri River)
- Gallatin County (Bozeman, Three Forks headwaters)
- Flathead Lake basin (Lake and Flathead counties)
- Bighorn River corridor and Crow Reservation
- Charles M. Russell National Wildlife Refuge
- Bitterroot Valley (Ravalli County)
Seasonal Activity Pattern
Biting starts in early to mid June across the eastern plains and irrigated valleys, peaks in July, and tapers fast through August. WNV cases concentrate in August across the Yellowstone Valley and the irrigated counties east of the divide. Cool nights at elevation hold daytime activity down even in midsummer, and the season collapses quickly with the first cold snap in September. Snowmelt off the Bitterroot, Mission, and Beartooth ranges produces brief floodwater Aedes pulses through June. The high country above timberline stays largely mosquito-free.
Monthly Biting Intensity (Mountain West)
Montana Mosquito Risk Profile
- WNV burden level
- Low
- about 10 to 25 confirmed cases annually
- EEE risk
- Rare
- Peak biting season
- June through August
- Top urban risk areas
- Billings (Yellowstone)
- Missoula (Missoula)
- Great Falls (Cascade)
- Bozeman (Gallatin)
Signature habitat: Yellowstone River bottoms, Flathead Lake wetlands, irrigated valleys, prairie potholes east of the divide.
Climate driver: Cx. tarsalis activity tracks irrigated agriculture; western mountain valleys see far less than eastern plains.
Check Your Local Mosquito Risk
Ready to see current mosquito activity in your area? Get today's forecast and personalized risk assessment for your ZIP code.
Common Mosquitoes in Montana
Understanding which mosquitoes are active in Montana 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 Montana
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 Montana?
Live water temperatures and swim conditions for Flathead Lake.
See Montana lake temperaturesWhen does mosquito season end in Montana?
Mosquito activity winds down after the first hard freeze, which in Montana typically arrives around Sep 22. See the local first-frost window and city-by-city freeze dates.
Montana first frost datesAlso worried about ticks in Montana?
Lyme disease risk and tick activity track different seasonal patterns than mosquitoes. See your Montana tick forecast.
View Montana tick forecastStay Safe in Montana
Get personalized mosquito forecasts and prevention tips for your area