Houston ranks among the top five worst cities in the United States for mosquito populations — a distinction earned by our unique geography, climate, and infrastructure. With over 56 named bayous running through Harris County, combined with frequent flooding events, dense residential landscaping, and an average annual temperature that rarely drops below mosquito-active thresholds, Houston offers mosquitoes nearly perfect breeding conditions for the majority of the year.
When Does Houston Mosquito Season Start?
The short answer: Houston mosquito season never fully ends. While activity drops during cold snaps in December and January, it never reaches zero the way it does in northern climates. The practical mosquito season — the period when outdoor activity is significantly impacted — runs from late February or early March through November. That's roughly nine months of mosquito pressure.
Monthly Mosquito Activity in Houston
- January–February: Low activity. Cold fronts suppress populations, but eggs overwinter in dried areas and hatch rapidly when temperatures rise
- March–April: Season begins. Temperatures above 50°F wake hibernating populations. Spring rains create widespread breeding sites
- May–June: Rapid population growth. Aedes aegypti (the primary dengue and Zika vector) becomes active as temperatures consistently exceed 70°F
- July–August: Peak season. Long days, heat, and standing water from summer storms drive maximum mosquito pressure
- September–October: Still heavy activity. Often the second-worst period as rainfall returns after summer dry spells
- November–December: Declining populations, but activity persists through warm fall days
Why Houston Is One of America's Worst Cities for Mosquitoes
The Houston bayou system — stretching over 2,500 miles across Harris County — was designed primarily for flood control, not aesthetics. While restoration projects have improved many bayous, slow-moving or stagnant water in the system provides enormous mosquito breeding habitat that cannot simply be eliminated. Add to this the drainage ditches required by Houston's flat topography, the collection of water in tree holes and landscape features throughout the region's abundant tree canopy, and the city's 52 inches of annual rainfall, and you have the ingredients for a year-round mosquito explosion.
Houston is also home to at least 56 mosquito species, including Aedes aegypti and Aedes albopictus (the Asian tiger mosquito), both capable of transmitting dengue fever, Zika virus, and chikungunya. Culex quinquefasciatus, the southern house mosquito, is the primary vector for West Nile virus in the region. Harris County Mosquito Control District conducts regular surveillance and aerial spraying programs, but these address the broadest infestations — individual property protection requires additional measures.
Finding and Eliminating Breeding Sites on Your Property
The most powerful thing you can do to reduce mosquito populations around your home costs nothing: eliminate standing water. Mosquitoes can complete their lifecycle from egg to biting adult in as few as 7 to 10 days in warm weather, and they breed in remarkably small amounts of water.
- Empty and scrub bird baths weekly — the scrubbing disrupts mosquito eggs attached to the sides
- Drain or treat any decorative water features that don't have pumps creating water movement
- Clear gutters of debris that causes water to pool rather than drain
- Turn over or store any outdoor containers, buckets, tarps, or toys that collect rainwater
- Address low spots in your yard where water pools for more than 48 hours after rain
- Change water in pet dishes and kiddie pools every few days
- Treat water features you cannot empty (ponds, rain barrels) with Bacillus thuringiensis israelensis (Bti) dunks — these are safe for people, pets, and wildlife
- Check for water trapped in tree holes, which can harbor significant mosquito populations
Personal Protection Strategies
- Use EPA-registered repellents containing DEET (20–30% concentration for adults), picaridin, or oil of lemon eucalyptus
- Wear long sleeves and light-colored clothing during peak mosquito hours (dusk and dawn for most species; all-day for Asian tiger mosquitoes, which bite in daylight)
- Install or repair window and door screens — a single gap is enough for significant indoor intrusion
- Run outdoor fans on patios and decks; mosquitoes are weak fliers and fans disrupt their ability to locate hosts
- Consider mosquito-proof screening for porches and outdoor entertaining areas
Professional Mosquito Treatment Options
For homeowners who want to genuinely reclaim their outdoor spaces, professional mosquito treatment delivers results that far exceed any DIY approach. The two main professional options are barrier spray programs and misting systems.
Barrier Spray Programs
A licensed technician applies a residual insecticide (typically a synthetic pyrethroid or bifenthrin-based product) to foliage, shrubs, and shaded areas where mosquitoes rest during the heat of the day. A single treatment provides 3 to 4 weeks of significant reduction. Monthly treatment programs through the mosquito season keep populations suppressed continuously. This is the most cost-effective professional option for most Houston homeowners.
Automatic Misting Systems
Fixed misting systems installed around a property's perimeter dispense timed doses of insecticide, typically at dawn and dusk when mosquito activity peaks. These systems provide consistent protection with minimal effort after installation, making them popular in Houston's high-end residential areas and for families with young children who need reliable daily protection.
Pro Tip
Tip: The best time to start professional mosquito treatment is February or March — before populations spike. Starting early disrupts the first generation of the season and results in significantly lower pressure throughout summer compared to starting treatment in June when populations are already established.
Disease Risk in Houston
West Nile virus is the primary mosquito-borne disease concern for most Houston residents. Harris County typically reports confirmed human cases every summer, and the risk is highest in late summer when Culex mosquito populations peak and birds (the reservoir host for West Nile) begin their fall migrations. Dengue fever is an emerging concern, with locally transmitted cases reported in Harris County in recent years as Aedes aegypti populations have grown. If you or a family member develops fever, rash, or severe headache in the days following significant mosquito exposure, consult a physician promptly.