Mosquito season in Union County, IA: when it starts and ends
Mosquito months in Union County
In a normal year mosquito season in Union County, IA starts around April 18 and ends around October 19, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Union 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 19.
- No West Nile cases since 2016, so bites in Union County are a nuisance; check window screens.
Union County against the rest of IA
Union County has the 36th longest season of 99 IA counties, at 184 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 48.9°F.
- Clarke County: April 18 to October 20 (185 days, 1 WNV)
- Keokuk County: April 18 to October 19 (184 days, 1 WNV)
- Black Hawk County: April 18 to October 18 (183 days, 0 WNV)
- Jasper County: April 18 to October 18 (183 days, 1 WNV)
West Nile in Union County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Union County (0 neuroinvasive) across 1 year. The worst was 2005 with 2; the latest was 2005.
See how the dates are worked out, and when the season starts across the US.