Today's Mosquito Risk in Arizona: 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 50 to 100 confirmed cases annually
- Phoenix metro drives most
- Based on CDC ArboNET surveillance data
- Risk Tier
- Tier 2: High Pressure
- North American Monsoon storms fill backyard washes and pool covers, triggering Aedes aegypti booms across Phoenix metro.
- Per mosquito-risk-model regional tier
- Highest-Risk Areas
- Maricopa, Pima (WNV and urban Aedes aegypti); Yuma and Pinal (Cx. tarsalis irrigated farmland)
Current Situation in Arizona
Arizona carries a moderate to high WNV burden of roughly 50 to 100 confirmed human cases annually, with the Phoenix metro driving most absolute case counts. The state runs as a monsoon-driven mosquito climate: from July through September, the North American Monsoon pushes moisture up from the Gulf of California into the Sonoran Desert, filling backyard washes, pool covers, and irrigated farm fields, and triggering explosive Aedes aegypti and Cx. quinquefasciatus booms across Phoenix and Tucson. Aedes aegypti is established urban statewide, with population centers in Phoenix (Maricopa), Tucson (Pima), and Yuma. Cx. quinquefasciatus dominates Culex WNV transmission across the urban metros. Cx. tarsalis fills in across the irrigated low desert farmland of Yuma, Pinal, and Maricopa counties. St. Louis Encephalitis remains a documented historic risk in the low desert. Aedes albopictus presence is limited. Biting season runs April through October, with peak monsoon activity July through September.
Snapshot of the current mosquito situation in Arizona, drawn from CDC ArboNET surveillance and the regional risk model.
- Risk Level
- High
- Peak Activity
- April through October
- Dominant Vector
- Yellow Fever Mosquito (Aedes aegypti) urban statewide; Southern House Mosquito (Culex quinquefasciatus)
Where Mosquitoes Breed in Arizona
Arizona mosquito habitat is built on the Sonoran Desert monsoon wash network and the irrigated low desert farmland. Phoenix metro neighborhoods across Maricopa County hold dense Aedes aegypti through backyard containers, pool covers, and ornamental water features, with the Salt River, Gila River, and Verde River corridors feeding sustained Cx. quinquefasciatus populations. Tucson and Pima County run a similar pattern at lower density, with Saguaro National Park bajadas seeing seasonal monsoon-driven Aedes pulses. The Yuma irrigated farmland along the lower Colorado River holds heavy Cx. tarsalis populations off lettuce and alfalfa fields through the warm season. The Salt River Valley irrigation grid feeds Mesa, Chandler, and Scottsdale Cx. quinquefasciatus. The Mogollon Rim country and the higher elevations of Flagstaff and the White Mountains run cool and largely mosquito-free. The Grand Canyon corridor stays drier than the low desert. Storm drains across Phoenix, Tucson, Mesa, Chandler, Scottsdale, and Yuma carry the urban Aedes aegypti and Cx. quinquefasciatus load.
Hotspot Counties & Areas
- Maricopa County (Phoenix, Mesa, Chandler, Scottsdale)
- Pima County (Tucson, Saguaro National Park bajadas)
- Yuma County (Yuma, lower Colorado River farmland)
- Pinal County (Casa Grande, Salt River Valley irrigation)
- Salt River corridor (Maricopa County)
- Gila River corridor (Pinal and Maricopa counties)
- Verde River corridor (Yavapai County)
- Mogollon Rim country (Coconino and Gila counties)
Seasonal Activity Pattern
Light biting begins in April across Phoenix and Yuma as warm-season Aedes aegypti populations stir, but the season breaks open with the North American Monsoon in early July. From July through September, monsoon thunderstorms fill desert washes, pool covers, and abandoned containers, triggering sharp Aedes aegypti and Cx. quinquefasciatus booms across Phoenix and Tucson. WNV cases concentrate from August through October across Maricopa and Pima counties, with secondary peaks in Pinal and Yuma. Cx. tarsalis populations on the Yuma and Salt River Valley farmland stay elevated through summer with the irrigation cycle. Aedes aegypti daytime biting runs from May through October, with peak intensity in August. The high country above 5000 feet stays largely mosquito-free. Failed monsoon years produce sharply lower transmission.
Monthly Biting Intensity (Southwest)
Arizona Mosquito Risk Profile
- WNV burden level
- High
- about 50 to 100 confirmed cases annually; Phoenix metro drives most
- EEE risk
- Rare
- Peak biting season
- July through October; monsoon-driven
- Top urban risk areas
- Phoenix (Maricopa)
- Tucson (Pima)
- Mesa (Maricopa)
- Chandler (Maricopa)
Signature habitat: Phoenix monsoon washes, Sonoran Desert arroyos, Salt River corridor, irrigated farmland.
Climate driver: North American Monsoon storms fill backyard washes and pool covers, triggering Aedes aegypti booms across Phoenix metro.
Check Your Local Mosquito Risk
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Common Mosquitoes in Arizona
Understanding which mosquitoes are active in Arizona helps you identify threats and take appropriate precautions. Click any card for details.
Southern House Mosquito
Culex quinquefasciatus
Risk: West Nile virus, St. Louis encephalitis, dog heartworm.
Key feature: Medium brown body with banded abdominal segments and no leg stripes.
Active: Year-round in the deep South; summer peak elsewhere. Most active from dusk through the first few hours after sunset.
Yellow Fever Mosquito
Aedes aegypti
Risk: Zika, dengue, yellow fever, chikungunya.
Key feature: Black body with white lyre-shaped markings on the thorax.
Active: Year-round in southern Florida and the Gulf; summer-only further north.
West Nile Virus
Vector: Southern House Mosquito
West Nile Virus
The most common mosquito-borne illness in the US. About 80% of infections cause no symptoms; less than 1% develop neuroinvasive disease.
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 Arizona
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.
When does mosquito season end in Arizona?
Mosquito activity winds down after the first hard freeze, which in Arizona typically arrives around Nov 15. See the local first-frost window and city-by-city freeze dates.
Arizona first frost datesAlso worried about ticks in Arizona?
Lyme disease risk and tick activity track different seasonal patterns than mosquitoes. See your Arizona tick forecast.
View Arizona tick forecastStay Safe in Arizona
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