Mosquitoes are already active in much of the United States. In the Gulf Coast, Florida, and Hawaii, they’ve been out since February. Across the South and inland Southwest, activity typically picks up in March. If you’re in the Mid-Atlantic, Great Lakes, or northern West, expect them by April. New England, the northern Midwest, and the Pacific Northwest usually see the first mosquitoes in May.
Where you live and what the weather has been doing in recent weeks are the two biggest factors. Here’s what determines whether mosquitoes are biting in your area right now and what you can do about it.
When Mosquitoes Emerge by Region
Mosquito season doesn’t flip on like a switch across the country. It rolls northward as temperatures warm:
- Gulf Coast, Florida, Hawaii: February
- South and inland Southwest: March
- Mid-Atlantic, Great Lakes, northern West: April
- New England, northern Midwest, Pacific Northwest: May
These are typical start dates. A warm spring pushes the timeline earlier; a cold, dry one delays it. In Minnesota, for example, the first mosquito larvae of 2025 were found on March 17, right on schedule. But cooler-than-average temperatures meant helicopter-based control treatments weren’t expected to begin until late April, a bit later than 2024.
Temperature and Rain Drive the Timeline
Mosquitoes need two things to get going: warmth and water. The earliest spring species lay eggs in low-lying ground depressions that fill with snowmelt and spring rain. As the water temperature rises enough for larvae to develop, those eggs hatch. This is why a warm, wet spring produces mosquitoes faster than a cool, dry one.
Rainfall patterns matter beyond just filling puddles. Years with heavy precipitation spread across multiple months tend to shift peak mosquito numbers earlier and can significantly increase total mosquito abundance for the year. Conversely, dry stretches suppress populations. Climate projections for summer 2025, for instance, suggest drier-than-normal conditions across parts of the Midwest from June through August, which could keep summer floodwater mosquito numbers relatively low.
The species you encounter also shifts with the calendar. The first mosquitoes of spring are typically single-generation species whose eggs survived winter in the soil and hatch as soon as snowmelt pools warm up. Later in the season, different species take over. Overwintering adult females wait until nighttime temperatures are warm enough to seek a blood meal and lay eggs, producing multiple generations through the summer. These later species, most active in summer and early fall, are also the ones most likely to carry diseases like West Nile virus.
Disease Risk Is Lowest Early in the Season
If you’re seeing the first mosquitoes of spring, the good news is that disease transmission risk is at its lowest point. Most mosquito-borne illnesses in the U.S. occur in summer and early fall, when mosquito populations peak and people spend the most time outdoors. Early-season mosquitoes are annoying, but they haven’t yet had the cycle of feeding on infected birds and animals that builds up virus levels in the population.
That changes as the season progresses. By midsummer, the risk of West Nile virus and other infections climbs. Projections for parts of the upper Midwest in 2025 suggest a potential mid-summer surge, with one regional model forecasting numbers similar to 2020, the last year a particular marsh-breeding species appeared in abundance.
How to Cut Mosquito Numbers Around Your Home
The single most effective thing you can do is eliminate standing water on your property. Mosquitoes can breed in as little as a quarter inch of water, and they don’t need a pond to do it. A forgotten bucket, a clogged gutter, or a bottle cap in the yard is enough.
Walk your property once a week and check these common culprits:
- Buckets, watering cans, cups, and other containers: Store inside, turn upside down, or drill drainage holes in the bottom.
- Old tires: Dispose of them. If used as playground equipment, drill holes so water drains out.
- Potted plant saucers: Remove them, empty them weekly, or fill them with fine aquarium gravel so water can’t pool.
- Kiddie pools: Empty or change the water every five to seven days. Store upside down or indoors when not in use.
- Pet water bowls: Rinse out weekly.
- Tarps, grill covers, and sandbox covers: Arrange so water runs off rather than collecting in folds. Keep grill vents closed.
- Gutters: Clean them so water flows freely, even “covered” types.
- Drainage ditches: Remove grass clippings and debris so water can drain.
- Hollow fence posts: Cap open chain-link or plastic fence posts.
- Wheelbarrows: Store upside down when not in use.
- Portable basketball hoops: Make sure the fill-hole caps are in place.
- Rain barrels: Cover with fine mesh screen.
- Dripping faucets or window AC units: Repair leaks or place rocks underneath so water runs off instead of puddling.
- Plastic weed barriers in gardens: Replace with landscape cloth that lets water pass through.
Consistency matters more than perfection. A single container left unchecked for a week can produce hundreds of mosquitoes. Making a quick lap around your yard part of your weekly routine is the most practical way to keep populations down before they build into a problem.