Mosquito season in Clayton County, IA: when it starts and ends
Mosquito months in Clayton County
In a normal year mosquito season in Clayton County, IA starts around April 27 and ends around October 11, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clayton County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 11.
- No West Nile cases since 2016, so bites in Clayton County are a nuisance; check window screens.
Clayton County against the rest of IA
Clayton County has the 93rd longest season of 99 IA counties, at 167 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 46.8°F.
- Winnebago County: April 26 to October 11 (168 days, 0 WNV)
- Allamakee County: April 27 to October 12 (168 days, 1 WNV)
- Fayette County: April 27 to October 11 (167 days, 1 WNV)
- Chickasaw County: April 27 to October 10 (166 days, 2 WNV)
West Nile in Clayton County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Clayton County (0 neuroinvasive) across 1 year. The worst was 2009 with 1; the latest was 2009.
See how the dates are worked out, and when mosquitoes go away for the winter.