Reliable signs you have mosquitoes in winter

• Itchy, single raised welts on exposed skin (ankles, wrists, neck), often after dusk or near plants/water.
• High‑pitched “whine” around ears in quiet rooms, basements, or garages.
• Adults resting on walls/ceilings: slim, long‑legged, narrow‑bodied; often in dark, humid spots near windows or drains.
• Larvae (“wrigglers”) in standing water: thin, comma‑shaped, hanging at the surface, darting down when disturbed.
• Pupae (“tumblers”) in water: small comma‑shapes that flip/tumble when tapped.
• Eggs: Culex egg “rafts” look like tiny black specks/rafts on water; Aedes eggs are single black seeds stuck just above the waterline inside containers.

Where to look indoors (even when it’s cold outside)

• Plant saucers, cut‑flower vases, pet bowls, humidifier or dehumidifier buckets, sump pits, floor drains, toilet tanks not often flushed.
• Uncovered rain barrels in attached garages, buckets, mop pails, or any container water sits in for 5–7 days.
• Warm rooms with sunlight and moisture (laundry rooms, boiler rooms, bathrooms).

Outdoor signs during mild spells (>10°C / 50°F)

• Buzzing or biting near south‑facing walls, sheds, woodpiles, or leaf litter on sunny afternoons.
• Larvae in snowmelt puddles, clogged gutters, tarps, buckets, wheelbarrows, birdbaths, and tree holes.
• Small dusk swarms over hedges/driveways after a warm day.

Common look‑alikes (not mosquitoes)

• Fungus gnats: tiny, weak fliers over potting soil; don’t bite.
• Drain flies: fuzzy, moth‑like insects lingering near sinks and showers.
• Midges: outdoor swarms that don’t bite; thicker bodies than mosquitoes.

Quick answer

Cut off water and entry points. Empty or treat any standing water with BTI, seal gaps and maintain tight screens, run fans, reduce indoor humidity, clean drains and trays, and use targeted traps or professional treatments if needed.

Why mosquitoes are around in winter

Many species survive as eggs in water or as adult females hiding in garages, sheds, basements, and warm rooms. Warm spells and heated spaces let them stay active.

Outdoors: remove breeding spots

• Dump water weekly: buckets, toys, plant saucers, tarps, grill covers, wheelbarrows.
• Clean gutters and drain flat roofs so water doesn’t pool.
• Cover rain barrels tightly with fine mesh; add BTI (Bacillus thuringiensis israelensis) dunks/granules to any water you can’t drain.
• Aerate ornamental ponds or use BTI; don’t rely on fish alone in cold temps.
• Store items upside down; stretch and secure tarps so they shed water.
• Keep sheds/garages as cold and dry as practical; close doors promptly.

Indoors: stop hiding and breeding

• Fix leaks; run a dehumidifier in damp basements to keep humidity under 50%.
• Empty and scrub plant saucers; change pet water daily.
• Pour hot water down seldom-used floor drains weekly; add BTI granules to sumps.
• Install/repair tight window and door screens; add door sweeps and weatherstripping.
• Use oscillating fans; mosquitoes avoid moving air.
• Vacuum resting adults on walls/ceilings.

Targeted controls

• Repellents on skin: EPA-registered DEET, picaridin, IR3535, or oil of lemon eucalyptus.
• Traps with CO₂ or heat/attractant can reduce adults in enclosed spaces; avoid UV zappers (kill non-targets).
• Residual insecticides on resting sites are effective but require label care; consider a licensed pro.