Mosquito Season Does Not End When Summer Does... Especially This Year
Late August is when most Southern California residents disengage from mosquito prevention. This year that instinct is worth reconsidering. NOAA's Climate Prediction Center reports El Niño is strengthening with a greater than 90% chance of a very strong event during fall and winter 2026–27, and above-normal temperatures are favored across much of the West into early September — conditions that keep mosquito breeding cycles active longer than residents typically expect. Compton Creek Mosquito Abatement District explains why the fall mosquito season in California extends beyond summer, what pet owners and outdoor exercisers need to know about late-season exposure, and how to request free mosquitofish in Compton, Lynwood, Paramount, and Rancho Dominguez before the season closes.
Late August is when most Southern California residents stop thinking about mosquitoes. School has started. Summer feels like it is winding down. Mosquito prevention drops off the mental checklist. This year, that instinct is worth reconsidering. The conditions driving mosquito activity this season have not wound down — and for residents in Compton, Lynwood, Paramount, and Rancho Dominguez, September is still very much part of mosquito season.
Why Late August 2026 Is Not the Time to Disengage
Three overlapping conditions are keeping mosquito breeding cycles active later into the summer than residents typically expect. None of them are unusual on their own. Together they create a late-season environment that is worth paying attention to.
NOAA's late-August outlook favors above-normal temperatures across much of the West into early September. Warm temperatures can accelerate mosquito development and allow breeding cycles to continue as long as standing water remains available.
Heat drives residents to water more frequently. More irrigation creates more opportunities for standing water to accumulate in flower pot saucers, low spots in garden beds, and drainage areas adjacent to residential properties.
NOAA's Climate Prediction Center reports El Niño is strengthening, with a greater than 90% chance of a very strong event during fall and winter 2026–27. El Niño does not directly cause mosquito activity, and its local effects can vary. What matters for mosquito breeding is whether warm conditions coincide with standing water — and in Southern California, irrigation, containers, and drains can provide that habitat even during dry periods.
The mechanism connecting heat to mosquito activity is indirect but consistent: sustained warmth keeps water temperatures elevated, which accelerates mosquito development when standing water is present. Remove the standing water and temperature becomes irrelevant. Leave it in place and a late-August heat wave becomes an extended breeding opportunity. That is why source reduction — emptying, tipping, covering — remains the most effective tool available regardless of what the season is doing.
The Myth: Mosquito Season Ends With Summer
The idea that mosquito season ends when school starts is one of the most persistent misconceptions in residential mosquito prevention. It is understandable — summer is when mosquito awareness peaks, when prevention campaigns run, and when most residents are thinking about it. But the biology does not follow that schedule.
Mosquito season ends in late August or early September when temperatures start to drop and summer winds down.
In Southern California, Culex mosquito activity can remain elevated through September and October. Warm temperatures, irrigation, and standing water sustain breeding conditions well into fall.
The practical consequence of this misconception is that late August and September become a period of reduced vigilance precisely when conditions may still support active mosquito populations. Yards go unchecked. Repellent stays home. The weekly source reduction habit that built up over the summer breaks down when residents feel the season is over.
The conditions that support mosquito activity have not ended — and prevention should not end either. Sustained temperatures, active irrigation, and a strengthening El Niño backdrop make this a year where the late-season window deserves attention rather than assumption.
Two Groups Worth a Specific Note This Month
Most mosquito prevention messaging focuses on families with young children, and for good reason. But late August introduces two additional resident groups whose outdoor patterns put them in contact with peak mosquito activity hours more than they may realize.
Dogs need walks regardless of the season — and the most comfortable walking hours during a heat wave are early morning and evening. Those windows overlap directly with increased Culex mosquito activity. Pets and their owners are outdoors together during the highest-exposure periods of the day, often near landscaping, drainage areas, and irrigation runoff that can support mosquito breeding.
- Apply EPA-registered repellent before early morning and evening walks in areas with vegetation or standing water nearby.
- Check your yard and walking route for standing water — drainage edges, low spots in landscaping, and containers along common walking paths.
- Report persistent standing water near parks, alleys, or drainage areas to CCMAD.
Heat waves push outdoor exercise toward the same morning and evening hours when Culex mosquitoes are most active. Physical exertion also increases the biological signals mosquitoes use to locate hosts: elevated body heat, increased carbon dioxide output, and perspiration. Outdoor runners, cyclists, and exercise groups are outdoors at the highest-exposure windows while producing stronger attractant signals than at rest.
- Apply EPA-registered repellent before outdoor workouts scheduled during dawn or dusk hours.
- Lightweight, loose-fitting long sleeves reduce exposed skin during dawn and evening workouts without significantly affecting comfort.
- Cool-down and stretching periods extend time outdoors at peak activity hours — apply repellent before, not after.
What to Keep Doing Through the End of the Season
The habits that reduced mosquito exposure earlier in the summer are the same ones that matter now. The only change is not letting the assumption that the season is over interrupt the habit.
Keep the Weekly Yard Check Going
The 5–7 day mosquito development cycle does not change in late August. A container left undisturbed for one week in warm weather is still enough time for a new generation of mosquitoes to develop. Walk your yard every week through the end of September. Flower pot saucers, gutters, bird baths, low spots in garden beds after watering, tarps, and outdoor furniture covers are the most commonly missed sites in late summer when irrigation remains active.
Keep Reporting Standing Water
Late summer irrigation often reveals standing water problems that were not visible earlier in the season — drainage edges, low spots in alleys, neglected containers in adjacent lots. If you notice persistent standing water on public property near your home, bus stop, or recreation area, report it to Compton Creek Mosquito Abatement District. We investigate.
Keep Repellent in Rotation
Repellent stays part of the routine for early morning and evening outdoor activities through September. Apply an EPA-registered repellent before spending time outdoors during early morning and evening hours. Oil of Lemon Eucalyptus (OLE) is a plant-based option recommended by the CDC for protection against mosquitoes that may carry West Nile Virus. For product-specific guidance and age restrictions, visit epa.gov/insect-repellents.
If you have an ornamental pond, water feature, or horse trough, Compton Creek Mosquito Abatement District provides mosquitofish at no cost to eligible residents in our service area. Mosquitofish provide ongoing biological control of mosquito larvae in suitable permanent water features. Up to 500 fish per household per day. Available now through the close of mosquito season. One call to request.
Request Free Mosquitofish →Found a Dead Bird? Keep Reporting.
Dead crows, ravens, and jays are indicators of West Nile Virus activity. Reporting continues to matter through September and into October. Call the California Dead Bird Reporting Hotline.
Mosquito Season Is Not Over. We Are Still Here.
Mosquito season does not end when summer does. If you are seeing increased mosquito activity near your home, have water sources you cannot eliminate, or want to request free mosquitofish before the season closes — contact Compton Creek Mosquito Abatement District now.
Contact CCMAD → Request Free Mosquitofish →El Niño and temperature outlook: NOAA Climate Prediction Center ENSO Diagnostic Discussion, August 13, 2026 (cpc.ncep.noaa.gov). West Nile Virus surveillance: cdph.ca.gov. Repellent guidance based on current CDC and EPA recommendations: epa.gov/insect-repellents.