Mosquito season in Decatur County, IA: when it starts and ends
Mosquito months in Decatur County
In a normal year mosquito season in Decatur County, IA starts around April 19 and ends around October 19, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Decatur County, and when
- Start tipping out standing water weekly by April 5.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 19.
- No West Nile cases since 2016, so bites in Decatur County are a nuisance; check window screens.
Decatur County against the rest of IA
Decatur County has the 39th longest season of 99 IA counties, at 183 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 50.7°F.
- Black Hawk County: April 18 to October 18 (183 days, 0 WNV)
- Jasper County: April 18 to October 18 (183 days, 1 WNV)
- Boone County: April 18 to October 18 (182 days, 3 WNV)
- O'Brien County: April 18 to October 18 (182 days, 5 WNV)
West Nile in Decatur County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Decatur County (1 neuroinvasive) across 1 year. The worst was 2003 with 1; the latest was 2003.
Background: when mosquitoes go away for the winter; how the dates are worked out.