Mosquito season in Butler County, IA: when it starts and ends
Mosquito months in Butler County
In a normal year mosquito season in Butler County, IA starts around April 22 and ends around October 15, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Butler County, and when
- Start tipping out standing water weekly by April 8.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 15.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk July to August, more so if over 60.
Butler County against the rest of IA
Butler County has the 62nd longest season of 99 IA counties, at 176 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 46.7°F.
- Sioux County: April 21 to October 14 (176 days, 32 WNV)
- Buena Vista County: April 22 to October 15 (176 days, 2 WNV)
- Grundy County: April 22 to October 15 (176 days, 2 WNV)
- Pocahontas County: April 22 to October 15 (176 days, 2 WNV)
West Nile in Butler County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Butler County (1 neuroinvasive) across 1 year. The worst was 2018 with 1; the latest was 2018.
Background: when mosquitoes go away for the winter; how the dates are worked out.