Mosquito season in Henry County, IA: when it starts and ends
Mosquito months in Henry County
In a normal year mosquito season in Henry County, IA starts around April 17 and ends around October 20, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Henry County, and when
- Start tipping out standing water weekly by April 3.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 20.
- 2 West Nile cases since 2016 (last 2018): you should use repellent at dusk July to August, more so if over 60.
Henry County against the rest of IA
Henry County has the 30th longest season of 99 IA counties, at 186 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 49.6°F.
- Adair County: April 17 to October 20 (186 days, 0 WNV)
- Clinton County: April 17 to October 19 (186 days, 3 WNV)
- Shelby County: April 17 to October 19 (185 days, 3 WNV)
- Washington County: April 17 to October 19 (185 days, 1 WNV)
West Nile in Henry County
From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Henry County (2 neuroinvasive) across 4 years. The worst was 2002 with 3; the latest was 2018.
Background: when mosquitoes go away for the winter; how the dates are worked out.