Where Mosquito Season Never Ends

No month below 50°F

In 22 counties the average temperature never falls below about 50°F and there is no normal hard freeze, so mosquitoes can be out any month of the year. By state: FL (14), HI (4), CA (3), TX (1).

Los Angeles County, CA; Orange County, CA; San Francisco County, CA; Broward County, FL; Charlotte County, FL; Collier County, FL; Hillsborough County, FL; Indian River County, FL; Lee County, FL; Manatee County, FL; Martin County, FL; Miami-Dade County, FL; Monroe County, FL; Orange County, FL; Pinellas County, FL; Polk County, FL; St. Lucie County, FL; Honolulu County, HI; Kalawao County, HI; Kauai County, HI; Maui County, HI; Cameron County, TX.

Almost all year

Another 99 counties have a season of 330 days or more, a few cool weeks in midwinter at most. The longest: Maricopa County, AZ (364 days); Galveston County, TX (364 days); Hidalgo County, TX (363 days); Willacy County, TX (363 days); Flagler County, FL (362 days); Palm Beach County, FL (362 days). For comparison, the median US county gets 206 days.

Year-round does not mean the same all year

Winter numbers are lower even where they never hit zero. The worst stretch is still summer, and in south Florida the wet season from June to October matters more than temperature. A dry winter means fewer breeding sites; a warm, rainy one can bring a burst.

What changes

There is no "before the season" moment to prepare for, so tipping water is a weekly habit all year, not a spring job. Dogs need heartworm prevention every month. Yard treatments make most sense ahead of the summer peak rather than year-round.

Where to go next

See the range: Hennepin County, MN · Cook County, IL · Harris County, TX · Miami-Dade County, FL.

How the Mosquito Season Dates Are Worked Out · When Does Mosquito Season Start? Dates Across the US