When does mosquito season end

Short answer

Mosquito activity drops sharply once temperatures fall below about 50 F, and it stops for the year after a hard frost kills the active adults. Because that turning point follows the cold, the end of mosquito season is a range rather than a date. In the northern tier it usually arrives in October, in the middle latitudes it stretches into November, and in the far south (South Florida and South Texas) it never fully arrives, so activity there continues year round (Defense Health Agency; Northeast Regional Climate Center, Cornell University).

The cold shutdown

Temperature, not the calendar, ends the season. When the air falls below roughly 50 F, mosquitoes stop flying and cannot feed, so bites taper off on cold nights even before the season truly closes (Defense Health Agency). A single cold night is only a pause. The season ends when cold becomes lasting.

The first hard freeze is the finish line for the active adults. Sub-freezing temperatures inhibit mosquito development and activity, and a freeze near 28 F counts as a relatively severe event, while a lighter frost near 32 F is generally less detrimental (Northeast Regional Climate Center, Cornell University). A hard freeze kills the mosquitoes that are still out flying and biting.

It does not, however, wipe out the species. Many mosquitoes survive winter in a dormant state. Some Culex females pass the cold months as adults in a reproductive pause called diapause, sheltering in places like sewers, culverts, sheds, basements, and animal burrows (Defense Health Agency; Meuti and colleagues, Journal of Medical Entomology). Others survive as cold-hardy eggs that wait for spring. So the freeze ends the biting season without ending the population.

Regional timing

Because the shutdown is tied to cold, the local first-frost and first-freeze dates drive when your season ends. Climate agencies publish average fall frost and freeze dates, along with the early and late extremes, and mosquito control programs use exactly these dates to plan the close of their operations (Northeast Regional Climate Center, Cornell University). As a rough guide, the first hard freeze reaches the northern states in October, the middle of the country through November, and the Gulf and southern coasts late or not at all.

At the far southern edge there is no reliable end. In South Florida, temperatures rarely drop to the 50 F threshold, and the University of Florida describes an active season running from roughly March through October with peak activity when temperatures sit in the upper 70s to 90s (University of Florida Emerging Pathogens Institute). Warm subtropical winters keep activity going in the deep south. In the Houston area, Harris County treats for mosquitoes year round as disease activity requires, rather than closing for a winter season (City of West University Place, Texas). South Texas and South Florida are best treated as year-round zones.

For where your area falls, see the regional guides linked under Related below.

Why they seem to come back

A cold snap can feel like the end, and then the bites return. That is normal. Diapausing adult females do not die in the cold. They hold in a paused state and resume activity when warmer temperatures return, so a mild spell in late fall or a warm winter day in the south can bring adults back out to fly (Defense Health Agency).

Fall itself is often busier than people expect. Warm days after summer rains, combined with the adults produced through late summer, can keep biting pressure high well past Labor Day and into the first cool weeks. Warm temperatures and rainfall create the conditions mosquitoes need, so an unusually warm and wet autumn extends the season rather than ending it (Centers for Disease Control and Prevention). The season is not over until the cold stays.

Do not stop prevention too early

The most common mistake is quitting in September. Because a warm autumn keeps adults active and standing water keeps producing new ones, prevention should continue until hard freezes are consistent in your area, and it should not stop at all in the year-round south.

Keep the routine simple through the fall. Once a week, empty, scrub, turn over, cover, or throw out anything that holds water, including buckets, planters, tarps, toys, birdbaths, and clogged gutters, since larvae and pupae grow in standing water (Centers for Disease Control and Prevention). When you are outdoors at dusk and dawn, keep using an EPA-registered repellent and wear long sleeves and pants (Centers for Disease Control and Prevention). Ending prevention before the cold does only hands the late-season adults an easy target.

Sources

1. Defense Health Agency, “Where Do Mosquitoes Go During the Winter?” (February 21, 2025). Government health source; states mosquitoes stop flying below 50 F and that females overwinter in diapause, resuming when warmer temperatures return. https://dha.mil/News/2025/02/21/14/50/Where-Do-Mosquitoes-Go-During-the-Winter (accessed 2026-07-20)
2. Northeast Regional Climate Center, Cornell University, “Frost” (mosquito planning resource). University climate center; states sub-freezing temperatures inhibit mosquito development and activity, defines freeze (28 F) and frost (32 F), and provides fall frost/freeze dates used for control planning. https://www.nrcc.cornell.edu/industry/mosquito/frost.html (accessed 2026-07-20)
3. University of Florida, Emerging Pathogens Institute, “Florida’s mosquitoes can make you sick: Here’s how to protect yourself” (May 1, 2024). University source; Florida mosquito season runs March to October, peak activity in the upper 70s to 90s. https://epi.ufl.edu/2024/05/01/floridas-mosquitoes-can-make-you-sick-heres-how-to-protect-yourself/ (accessed 2026-07-20)
4. Meuti M.E. and colleagues, “Overwintering Biology of Culex (Diptera: Culicidae) Mosquitoes in the Sacramento Valley of California,” Journal of Medical Entomology 50(4):773 (2013). Peer-reviewed; Culex females overwinter as adults in diapause. https://academic.oup.com/jme/article/50/4/773/889947 (accessed 2026-07-20)
5. Meuti M.E. and colleagues, “Functional circadian clock genes are essential for the overwintering diapause of the Northern house mosquito, Culex pipiens,” Journal of Experimental Biology 218(3):412 (2015). Peer-reviewed; shortening day length programs the overwintering diapause. https://journals.biologists.com/jeb/article/218/3/412/14463/Functional-circadian-clock-genes-are-essential-for (accessed 2026-07-20)
6. Centers for Disease Control and Prevention, “Mosquito Control at Home” and “Preventing Mosquito Bites.” Federal public health guidance; empty and scrub standing water weekly, use EPA-registered repellents and protective clothing. https://www.cdc.gov/mosquitoes/mosquito-control/mosquito-control-at-home.html and https://www.cdc.gov/mosquitoes/prevention/index.html (accessed 2026-07-20)
7. City of West University Place, Texas, “Mosquito Control.” Municipal page in the Harris County area; Harris County treats year round as needed based on disease activity. https://westutx.gov/271/Mosquito-Control (accessed 2026-07-20)

Related

• When does mosquito season start [placeholder]
• Mosquito season by region [placeholder]
• Mosquito season in Florida [placeholder]
• Mosquito season in Texas [placeholder]
• How weather and temperature affect mosquitoes [placeholder]

Educational note: This page is a general reference for planning and awareness. It is not medical, pest-control, or public-health advice for a specific situation. For local timing, follow your regional mosquito control program and public health department.

Last reviewed 20 July 2026.