Mosquito season in Worth County, IA: when it starts and ends

Mosquito months in Worth County

In a normal year mosquito season in Worth County, IA starts around April 30 and ends around October 7, about 23 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Worth County, and when

• Start tipping out standing water weekly by April 16.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 7.
• No West Nile cases since 2016, so bites in Worth County are a nuisance; check window screens.

Worth County against the rest of IA

Worth County has the 99th longest season of 99 IA counties, at 160 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 43.4°F.

• Osceola County: April 28 to October 11 (166 days, 2 WNV)
• Howard County: April 29 to October 10 (164 days, 0 WNV)

West Nile in Worth County

CDC ArboNET lists no human West Nile cases for Worth County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 4 of those years.

See how the dates are worked out, and when mosquitoes go away for the winter.