Mosquito season in Clarke County, IA: when it starts and ends
Mosquito months in Clarke County
In a normal year mosquito season in Clarke County, IA starts around April 18 and ends around October 20, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clarke County, and when
- Start tipping out standing water weekly by April 4.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 20.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk June to August, more so if over 60.
Clarke County against the rest of IA
Clarke County has the 34th longest season of 99 IA counties, at 185 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 49.7°F.
- Washington County: April 17 to October 19 (185 days, 1 WNV)
- Adams County: April 18 to October 19 (185 days, 2 WNV)
- Keokuk County: April 18 to October 19 (184 days, 1 WNV)
- Union County: April 18 to October 19 (184 days, 0 WNV)
West Nile in Clarke County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Clarke County (1 neuroinvasive) across 4 years. The worst was 2018 with 1; the latest was 2018.
See how the dates are worked out, and when mosquitoes go away for the winter.