A month-by-month mosquito checklist

Short answer

There is one thing worth doing in every part of the year, and the whole calendar comes down to it: deny mosquitoes the standing water they breed in, and protect yourself when they are flying. In late winter and early spring, scout and clear breeding sites before broods hatch. In late spring, start dumping standing water every week and treat water you cannot drain. Through summer and into early fall, keep that weekly habit going while using repellent and protecting yourself at dawn and dusk. In late fall and winter, clean up and prepare for next year.

Timing slides with the thermometer, not the month. Mosquitoes become active once daytime temperatures hold above roughly 50 degrees Fahrenheit, so the season opens earlier in the south and later in the north (Source 6). Read the calendar below as a shape, then shift it earlier if you live in the south and later if you live in the north. For the trigger that starts it all, see when mosquito season starts, and for local timing browse the region pages.

Here is the year at a glance. The right-hand column is the single most useful action for that stretch.

Late winter and early spring

This is the quiet, high-leverage window. The mosquitoes you prevent now are the ones you never have to swat in July. Two groups are waiting for warmth: adult females of some Culex species that survived winter in sheltered spots, and Aedes eggs laid last fall that hatch once water covers them. Both depend on standing water, so clearing that water before it warms up is the single best move of the year.

Checklist for this window:

• Walk the whole property and inventory anything that holds water: buckets, plant saucers, toys, tarps, wheelbarrows, old tires, clogged gutters, and bird baths (Sources 1, 5).
• Throw away trash that collects water, and drill drainage holes in tire swings and similar items so they cannot pool (Source 5).
• Store toys, watering cans, and containers in a shed or garage, or turn them upside down so they stay dry (Source 5).
• Stock a repellent now so you are not caught short. The CDC recommends EPA-registered repellents with active ingredients such as DEET, picaridin, or IR3535 (Source 2).

Remember that mosquitoes become active once temperatures hold above about 50 degrees Fahrenheit, and eggs start to hatch once that threshold is sustained (Source 6). In the far south this can happen in February or even earlier, so start sooner if you live there.

Late spring

Once the season opens, the goal shifts from cleanup to routine. Mosquitoes can go from egg to biting adult in about a week, which is exactly why the core habit is weekly (Source 5).

Checklist for late spring:

• Begin the weekly habit: at least once a week, empty, scrub, turn over, cover, or throw away anything that holds water (Sources 1, 5). Scrubbing matters because eggs stick to container walls.
• For water you cannot drain, such as rain barrels, ornamental ponds, or low spots that stay wet, treat with Bti (Bacillus thuringiensis subspecies israelensis). Bti is a naturally occurring soil bacterium that kills mosquito larvae in standing water and has no toxicity to people (Source 4). It is sold for home use as dunks and granules (Source 5).
• Repair torn screens on windows and doors, and use air conditioning where you have it, so mosquitoes stay outside (Source 2).

Doing this before the population builds keeps the whole summer easier to manage. For the full method, see source reduction and eliminate standing water.

Summer

Summer is peak vigilance. Warmth speeds up development, populations are highest, and biting is at its worst. Nothing here is new, it is the late-spring routine held steady and paired with personal protection.

Checklist for summer:

• Keep the weekly source-reduction habit going without a break (Sources 1, 5). One skipped week is enough time for a new brood to emerge.
• Re-treat water you cannot drain with Bti on the schedule the product label specifies (Source 4).
• Use EPA-registered repellent whenever you are outside for a while (Source 2).
• Wear loose, long-sleeved shirts and pants when practical, and consider clothing treated with permethrin (Source 2).
• Run a fan on patios and porches. Mosquitoes are weak fliers, and moving air makes it harder for them to reach you.
• Take extra care at dawn and dusk, when many species bite most, and cover up or move indoors during those windows.

Late summer and early fall

Do not relax here. This is the stretch where mosquito-borne disease risk is highest, even as the weather starts to feel like fall. West Nile virus, the most common mosquito-borne illness in the country, circulates through summer and into fall, and the number of people diagnosed typically peaks in late August to early September (Source 3).

Checklist for this window:

• Keep every summer habit going: weekly water dumping, Bti on undrainable water, repellent, and protection at dawn and dusk (Sources 1, 2, 4, 5).
• Pay attention to local advisories. Your state or local health department issues guidance when West Nile or other viruses are active in your area (Source 3).
• Resist the urge to quit early. Warm early-fall days keep mosquitoes flying, and this is precisely when the disease risk is greatest. For more, see the fall surge and when mosquito season ends.

Late fall and winter

As nights cool and mosquitoes go dormant, the work shifts to cleanup and setting up next year to be easier. The eggs laid this fall are the broods you will face next spring, so denying them water now pays off later.

Checklist for late fall and winter:

• Clean leaves and debris out of gutters so water drains freely rather than pooling, and check that downspouts do not leave standing water at ground level (Source 5).
• Empty every container that could collect winter and spring rain, then store it upside down or under cover so it stays dry (Source 5).
• Remove or drain low spots, tarps, and anything else that holds water through the cold months.
• Note what bred mosquitoes this year, that chronically wet corner or the pot you kept forgetting, and plan to fix it before next season.

In the far south, where temperatures rarely stay below 50 degrees for long, some mosquitoes stay active through winter, so keep the weekly habit going year-round there (Source 6). For where mosquitoes go in the cold, see winter: where they go and overwintering and diapause.

Sources

1. Centers for Disease Control and Prevention, “Mosquito Control at Home.” https://www.cdc.gov/mosquitoes/mosquito-control/mosquito-control-at-home.html (accessed 20 July 2026). (Once a week, empty, scrub, turn over, cover, or throw away items that hold water, such as tires, buckets, planters, toys, pools, bird baths, and trash containers; treat standing water that cannot be dumped to control larvae. Page returned HTTP 403; wording confirmed via the CDC search result summary.)
2. Centers for Disease Control and Prevention, “Preventing Mosquito Bites.” https://www.cdc.gov/mosquitoes/prevention/index.html (accessed 20 July 2026). (Use EPA-registered insect repellents with active ingredients such as DEET, picaridin, or IR3535; wear loose, long-sleeved shirts and pants; use permethrin-treated clothing; and control mosquitoes indoors and outdoors.)
3. Centers for Disease Control and Prevention, “About West Nile Virus.” https://www.cdc.gov/west-nile-virus/about/index.html (accessed 20 July 2026). (West Nile virus season runs from summer into fall; the number of people diagnosed typically peaks in late August to early September. Page returned HTTP 403; wording confirmed via the CDC search result summary.)
4. United States Environmental Protection Agency, “Bti for Mosquito Control.” https://www.epa.gov/mosquitocontrol/bti-mosquito-control (accessed 20 July 2026). (Bti is a naturally occurring soil bacterium whose toxins specifically target mosquito, blackfly, and fungus gnat larvae; it is applied to standing water where larvae are found and has no toxicity to people.)
5. University of Maryland Extension, “The 4 E’s for Easy, Breezy, Beautiful Mosquito Source Reduction.” https://marylandgrows.umd.edu/2023/06/30/the-4-es-for-easy-breezy-beautiful-mosquito-source-reduction/ (accessed 20 July 2026). (Eliminate, exchange, or empty water-holding containers at least once weekly because larvae develop into adults within about a week; store items in a shed or garage; drill drainage holes in tire swings; apply Bti to water that cannot be removed; clean gutters.)
6. University of Florida IFAS Extension (DeSoto County), “Ditch the Itch: Tips for Mosquito Season in Florida.” https://blogs.ifas.ufl.edu/desotoco/2025/04/16/ditch-the-itch-tips-for-mosquito-season-in-florida/ (accessed 20 July 2026). (Mosquitoes become active and dormant eggs begin to hatch once temperatures hold consistently above about 50 degrees Fahrenheit; timing therefore arrives earlier in warmer regions.)

Related

• Seasons overview: Mosquito seasons
• Season start: When does mosquito season start
• Season end: When does mosquito season end [placeholder link]
• Fall risk: The fall surge
• Control: Source reduction
• Control: Eliminate standing water
• Regions index [placeholder link]

Educational note: This page is for general information only and is not medical advice. It is not affiliated with any government agency or product. If you think you may have a mosquito-borne illness, contact a healthcare provider, and consult your state or local health department for current advisories.

Last reviewed 20 July 2026.