When Do Mosquitoes Go Away? The End of the Season
Cool days first, then the freeze
Biting drops off as the mean temperature falls below about 50°F, and a hard freeze near 28°F kills most adults still flying. A county's season on this site ends at whichever of the two comes first in a normal year. A light frost at 32°F does not end it; mosquitoes shelter and come out again on the next warm afternoon.
End month, county by county
| Season ends in | Counties | Share |
|---|---|---|
| January | 110 | 4% |
| August | 12 | 0% |
| September | 177 | 6% |
| October | 1,474 | 47% |
| November | 1,121 | 36% |
| December | 224 | 7% |
A January end means the season wraps into the new year in the far south. The other 8 have no hard-freeze record nearby and are dated on temperature alone.
Where they go
They do not die out. Aedes mosquitoes leave eggs that sit dry through the winter and hatch with the first spring rain. Female Culex, the main West Nile carrier, spend the winter as adults in sheltered spots: garages, crawlspaces, storm drains, sheds. A mosquito in the garage in January is one of them, and it is not a sign the season has started.
What you can put away, and when
Repellent and yard treatments can stop at the end date on your county page. Keep emptying anything that holds water into autumn: the last generation of the year lays the eggs that start next spring. Clearing gutters and turning over containers before winter is the cheapest head start on the next season.
Where to go next
See the range: Hennepin County, MN · Cook County, IL · Harris County, TX · Miami-Dade County, FL.
West Nile Virus by County: How to Read the Case Counts · Where Mosquito Season Never Ends