When Do Mosquitoes Go Away? When Mosquito Season Ends, by Region

Mosquitoes go away when the weather stays cold, not on a set date. They slow down below about 60°F (15°C), most stop flying below about 50°F (10°C), and a hard frost followed by steady cold ends the season. In much of the United States that comes weeks after Labor Day; in south Florida, mosquitoes bite almost all year.

The question is understandable: after months of swatting, spraying and relighting, everyone wants to know when it ends. The answer has two parts. The first is biology: mosquitoes are cold-blooded, so they disappear when temperatures fall below the levels that shut down flying, feeding and breeding, and across much of North America that happens later than people assume.

The second is risk: West Nile virus activity runs through the summer and into the fall, so the weeks when many households pack away their repellent can be the riskiest of the year. If you use coils on the patio, our complete guide to mosquito coils explains how they work and how to use them.

In this guide:

• When Does Mosquito Season End? A Region-by-Region Guide
• What Temperature Do Mosquitoes Die — and What Temperature Just Slows Them Down?
• Late-Season Diseases to Watch: West Nile, EEE and La Crosse
• Do Mosquitoes Die in Winter? Where Mosquitoes Actually Go When It Gets Cold
• Why Some Seasons Are Worse: What West Nile Case Counts Show
• Dengue and Day-Biting Mosquitoes: Why Dusk-Only Protection Falls Short
• The Late-Season Protection Checklist: Keep This Running Until the First Hard Frost
• So, When Do Mosquitoes Go Away?

There is no national end date for mosquito season. It ends when sustained cool weather arrives, and that moment moves across North America over about three months:

Canada is not the mosquito-free exception it is often assumed to be. West Nile virus is reported there every year, most cases occur in Ontario and Quebec, most people fall ill in August and September, and older adults are most affected, according to the Public Health Agency of Canada. A short season is not a harmless one.

Two caveats matter. First, these windows have been stretching: warmer autumns keep evenings in the range where mosquitoes stay active later into the year (see the dated box further down). Second, the end of biting weather is not the end of risk in any given week. Late summer is when West Nile activity is usually highest, so August and September deserve more caution than June, not less.

The question of what temperature kills mosquitoes hides two different numbers. Mosquitoes are cold-blooded, so their activity follows the air around them. As a working rule of thumb used by entomologists and mosquito-control programs, mosquitoes turn sluggish as temperatures drop toward about 60°F (15°C), and below about 50°F (10°C) most species can no longer fly or feed well. At that point they either die or go dormant.

Those numbers describe sustained conditions, not one chilly night. A light frost in early October kills some exposed adults, but the survivors bite again on the next warm afternoon. That is why a single cold snap never ends the season and a warm spell can bring mosquitoes back in mid-fall. What closes the season is a hard, killing frost followed by consistently cool days and nights.

Even then, freezing temperatures kill only the mosquitoes caught in the open. Adults that have found shelter, and eggs laid in soil or containers, survive far colder weather, which is why the same backyard fills with mosquitoes again every spring.

On cool late-season days, activity also bunches into the milder hours around dusk, so the evenings you spend on the patio can be the riskiest hours. Temperature tells you when mosquitoes stop flying, not when they stop existing.

West Nile virus is what most people mean when they worry about late-season bites, but two rarer viruses are worth knowing because they can be severe:

• West Nile virus is the leading cause of mosquito-borne disease in the contiguous United States, and its activity typically runs through the summer and into the fall (CDC). It is spread mainly by Culex mosquitoes, which bite most from dusk to dawn.
• Eastern equine encephalitis (EEE) is rare: an average of 11 human cases a year are reported in the United States, mostly near freshwater hardwood swamps in the Atlantic and Gulf Coast states and the Great Lakes region (CDC data). About 30% of people who develop severe EEE die, and many survivors have lasting neurologic problems (CDC).
• EEE can turn up in new places: in 2024 Vermont recorded its first human cases since 2012 (MMWR).
• La Crosse virus causes 30 to 90 reported cases of neuroinvasive disease in the United States each year (CDC data). Severe disease occurs most often in children under 16, and most cases occur in the upper Midwestern, mid-Atlantic and southeastern states (CDC).
• La Crosse is spread mainly by the eastern treehole mosquito (Aedes triseriatus), an aggressive daytime biter that breeds in tree holes and in containers such as discarded tires (CDC).

The practical point: an evening-only routine does not cover a day-biting mosquito that breeds in the tire, bucket or blocked gutter in your own yard. Emptying standing water and protecting yourself in daylight matter as much as the hours around dusk.

Individually, most do; the population never does, because different species carry different survival equipment into the cold. Culex mosquitoes, the main carriers of West Nile virus, spend the winter as adults. Mated females enter a hibernation-like state called diapause and shelter in basements, outbuildings and underground spaces, living on stored fat until spring, while the males die (Rutgers Center for Vector Biology). So where do mosquitoes go in winter? Often a few dozen feet from your back door.

Aedes mosquitoes, including the day-biting species that spread dengue, mostly survive the winter as eggs. Females lay them on the inner walls of containers just above the waterline. According to the CDC, the eggs can survive drying out for up to eight months, and even a winter in the southern United States; once water covers them, an egg can become a biting adult in 7 to 10 days.

Some species even spend the winter as larvae under the ice of frozen ponds (N.C. Cooperative Extension).

This also answers how long mosquitoes live. In summer an adult female usually lives a few weeks, long enough for several bite-and-lay cycles, and males live much less. A female in diapause can last the whole winter, which is how spring populations restart so quickly.

The practical lesson falls in autumn: every bucket, tarp fold, clogged gutter and plant saucer you empty in October removes eggs that would hatch next spring, which makes fall cleanup the cheapest mosquito control there is.

If one summer feels worse than another, surveillance data usually agree. West Nile case counts swing widely from year to year with the weather, the birds that carry the virus and the number of mosquitoes. A season that starts early still has its busiest weeks ahead of it, because cases usually build into late summer.

West Nile also does not follow the map most people expect. In 2025 the states with the most reported cases were Colorado, Illinois and Texas, not Florida (CDC historic data). The heaviest burden sits in the Mountain West and the Midwest as much as in the South, so late-season precautions matter across the whole continent.

West Nile is not the only late-season concern. Dengue is spread by Aedes mosquitoes, container breeders that live close to houses and bite during the day. The CDC reports limited local spread of dengue in Florida, Hawaii, Texas, Arizona and California, while rating the risk of widespread transmission in the continental United States as low. In Puerto Rico, a US territory, the CDC classes dengue risk as frequent or continuous (CDC).

Locally acquired means the patient did not catch dengue abroad: they were bitten at home by local mosquitoes that already carried the virus. Florida's county health departments issue mosquito-borne illness advisories when that happens, as Hillsborough County did on July 28, 2026 (Florida Department of Health).

Local spread also reaches beyond the subtropics. In Los Angeles County, investigators confirmed 14 locally acquired cases between August and November 2024, and in one neighborhood transmission continued for up to seven weeks (Emerging Infectious Diseases).

A routine built entirely around dusk, which suits the Culex mosquitoes behind West Nile, has a blind spot exactly where dengue mosquitoes operate, so households in Aedes territory should plan for an all-day season. Storms matter too: heavy rain or a hurricane floods eggs that have been waiting dry, and a new wave of mosquitoes can follow within about two weeks, so clear standing water after every storm.

Here is a sensible routine from now until temperatures stay cold:

1. Empty standing water every week: plant saucers, buckets, tarps, toys, birdbaths and clogged gutters. Container-breeding mosquitoes can go from egg to adult in 7 to 10 days of warm weather.
2. Check window screens and door sweeps before mosquitoes start looking for winter shelter in sheds, garages and basements.
3. Match your protection to the mosquitoes around you: dusk and dawn for the Culex mosquitoes that spread West Nile, plus daytime hours where Aedes mosquitoes live.
4. Use an EPA-registered skin repellent when you are outdoors under heavy mosquito pressure; it remains the best-studied personal protection.
5. Watch local advisories. County and city mosquito-control programs publish spraying schedules and positive test results.
6. Be realistic about repellent plants. Citronella, lemongrass and geranium look pleasant on a deck, but a potted plant releases very little of its oil into the air.
7. For patio and campsite evenings, a mosquito coil can treat the air around a seating area. Follow the label and buy a registered product. Burn it outdoors only, never in a tent, closed porch or garage, and light it 15 to 20 minutes before you sit down. Our guide to mosquito repellent for the yard, patio and campsite covers placement in more detail, or see the coil types we make.
8. Use a coil with care: place it out of the wind on a metal holder on a non-combustible surface, at least 1 m (about 3 feet) from anything flammable and out of reach of children and pets. Keep the smoke away from babies and young children, pregnant women, anyone with asthma, COPD or heart disease, cats and pet birds, and put the coil out before you go inside or to sleep.
9. Do not pack the kit away on a calendar date. Keep it until night-time temperatures stay below about 50°F (10°C).

Mosquitoes go away when cold weather settles in: they slow down below about 60°F (15°C), most stop flying below about 50°F (10°C), and a hard frost followed by steady cold ends the season. In most of the United States that means weeks after Labor Day; along the Gulf Coast and in south Florida it may be close to never.

Until then, late summer is the riskiest stretch for West Nile, so keep emptying standing water, keep repellent at hand and use any coil outdoors only, putting it out before you go to sleep.

Brands and retailers planning their own range can read about OEM and private-label mosquito coil manufacturing.