MosquitoMonths

When does mosquito season start and end where you live?

Mosquitoes switch on when nights stay warm and switch off after the first hard cold. Look up your county to see the months they are usually active there, when the peak hits, and how often mosquito-borne illness has been reported nearby.

Same insect, very different calendars

Mosquitoes start biting once the average day holds above about 50°F and stop at the first hard freeze. In 29% of counties that leaves six months or less. In 22 counties, almost all in south Florida, Hawaii and coastal California, it never really stops.

Months mosquitoes are normally active, darkest at the peak
CountyJanFebMarAprMayJunJulAugSepOctNovDecSeason
King, WA on on on on on early May to early October
Hennepin, MN on on peak peak on late April to mid October
Denver, CO on on peak peak on on late April to mid October
Cook, IL on on peak peak on on mid April to late October
Fulton, GA on on on peak peak peak peak on on early March to mid November
Harris, TX on on on peak peak peak peak peak peak peak on on Nearly all year (49 wk)
Maricopa, AZ on on on peak peak peak peak peak peak peak on on Nearly all year (52 wk)
Miami-Dade, FL on on peak peak peak peak peak peak peak peak peak on All year

Do this 14 days before your start date

Eggs laid in standing water become biting adults in one to two weeks once it is warm, so the cheapest fix lands just before the season, not in the middle of it.

  • Tip anything holding water: saucers, buckets, tarps, toys, clogged gutters. Once a week all season.
  • For water you cannot tip, like a rain barrel or a pond, drop in a Bti larvicide dunk. It kills larvae and leaves fish, pets and birds alone.
  • If you pay for yard spraying, book the first visit for that date. Spraying before then mostly hits nothing.

West Nile is the illness mosquitoes most often carry in the US. Each county page shows how many human cases CDC has recorded there since 1999, a count rather than a rate, so big counties look worse partly because more people live in them.