Today's Mosquito Risk in Utah: 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
- Bear River and Salt Lake basin wetlands sustain Cx. tarsalis; high desert plateaus stay sparse.
- Per mosquito-risk-model regional tier
- Highest-Risk Areas
- Salt Lake, Davis, Weber, Utah (Wasatch Front); Box Elder (Bear River refuge); Washington (Virgin River, southern Utah)
Current Situation in Utah
Utah carries a low WNV burden of roughly 10 to 25 confirmed human cases annually, with risk concentrated along the Wasatch Front from Ogden through Salt Lake City and Provo and around the Great Salt Lake basin wetlands. Cx. tarsalis is the dominant vector statewide, with population centers tied to the Bear River Migratory Bird Refuge, Antelope Island, and the Salt Lake basin marshes. Cx. quinquefasciatus fills in across southern Utah and the warm Virgin River corridor around St. George. Cx. pipiens carries the urban storm drain load in Salt Lake City and Provo. Aedes aegypti and Aedes albopictus are not established. EEE is rare. The Wasatch and Uinta Mountains run too cold for meaningful arboviral transmission, and the high desert plateaus across the southeast stay sparse. Biting season runs June through September.
Snapshot of the current mosquito situation in Utah, 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 Utah
Utah mosquito habitat is built on the Great Salt Lake basin wetlands and the Wasatch Front urban grid. The Bear River Migratory Bird Refuge at the north end of the Great Salt Lake holds tens of thousands of acres of marsh that produces sustained summer Cx. tarsalis populations and feeds the bird-amplification cycle behind regional WNV transmission. Antelope Island state park and the Farmington Bay waterfowl area carry the same pattern at lower density. Cache Valley around Logan holds irrigated pasture and dairy habitat with steady summer Cx. tarsalis. The Wasatch Front urban storm drain grid through Salt Lake City, West Valley City, West Jordan, Sandy, Provo, and Ogden carries the Cx. pipiens load. The Virgin River corridor around St. George and the lower Colorado River through Lake Powell hold warm-season Cx. quinquefasciatus. The Uinta Mountains, the Wasatch high country, and the canyons of Bryce and Zion run too cool or too dry for sustained populations.
Hotspot Counties & Areas
- Salt Lake County (Salt Lake City, West Valley City, West Jordan)
- Utah County (Provo, Utah Lake margins)
- Weber County (Ogden)
- Davis County (Farmington Bay, Wasatch Front)
- Bear River Migratory Bird Refuge (Box Elder County)
- Antelope Island state park
- Cache Valley (Cache County)
- Virgin River corridor (Washington County, St. George)
Seasonal Activity Pattern
Biting starts in early to mid June across the Wasatch Front and the Great Salt Lake basin marshes, peaks through July and August, and tapers through September. WNV cases concentrate in August across Salt Lake, Davis, Weber, and Utah counties. Cx. tarsalis populations on the Bear River refuge and the Salt Lake basin marshes stay elevated through summer with the wetland cycle. Snowmelt off the Wasatch and Uintas produces sharp floodwater Aedes pulses through late June on the canyon trails. The southern Utah corridor around St. George runs a few weeks ahead of the Wasatch Front on phenology, with Cx. quinquefasciatus active from May through October. Cool nights at elevation hold high country activity down.
Monthly Biting Intensity (Mountain West)
Utah Mosquito Risk Profile
- WNV burden level
- Low
- about 10 to 25 confirmed cases annually
- EEE risk
- Rare
- Peak biting season
- June through September
- Top urban risk areas
- Salt Lake City (Salt Lake)
- West Valley City (Salt Lake)
- Provo (Utah)
- Ogden (Weber)
Signature habitat: Wasatch Front urban, Bear River refuge, Antelope Island wetlands, Utah Lake margins.
Climate driver: Bear River and Salt Lake basin wetlands sustain Cx. tarsalis; high desert plateaus stay sparse.
Check Your Local Mosquito Risk
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Common Mosquitoes in Utah
Understanding which mosquitoes are active in Utah 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 Utah
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 Utah?
Live water temperatures and swim conditions for Lake Powell.
See Utah lake temperaturesWhen does mosquito season end in Utah?
Mosquito activity winds down after the first hard freeze, which in Utah typically arrives around Oct 8. See the local first-frost window and city-by-city freeze dates.
Utah first frost datesAlso worried about ticks in Utah?
Lyme disease risk and tick activity track different seasonal patterns than mosquitoes. See your Utah tick forecast.
View Utah tick forecastStay Safe in Utah
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