Mosquito season in Hamilton County, IA: when it starts and ends
Mosquito months in Hamilton County
In a normal year mosquito season in Hamilton County, IA starts around April 24 and ends around October 12, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Hamilton County, and when
- Start tipping out standing water weekly by April 10.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 12.
- No West Nile cases since 2016, so bites in Hamilton County are a nuisance; check window screens.
Hamilton County against the rest of IA
Hamilton County has the 84th longest season of 99 IA counties, at 171 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 46.2°F.
- Delaware County: April 24 to October 13 (172 days, 0 WNV)
- Dickinson County: April 24 to October 13 (172 days, 1 WNV)
- Benton County: April 25 to October 12 (170 days, 0 WNV)
- Lyon County: April 25 to October 12 (170 days, 19 WNV)
West Nile in Hamilton County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Hamilton County (2 neuroinvasive) across 2 years. The worst was 2013 with 1; the latest was 2013.
Background: when mosquitoes go away for the winter; how the dates are worked out.