Mosquito season in Story County, IA: when it starts and ends
Mosquito months in Story County
In a normal year mosquito season in Story County, IA starts around April 19 and ends around October 17, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Story 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 17.
- 8 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Story County against the rest of IA
Story County has the 44th longest season of 99 IA counties, at 181 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 48.1°F.
- Harrison County: April 19 to October 18 (182 days, 7 WNV)
- Iowa County: April 19 to October 17 (181 days, 0 WNV)
- Carroll County: April 20 to October 18 (181 days, 3 WNV)
- Greene County: April 20 to October 17 (180 days, 2 WNV)
West Nile in Story County
From 1999 to 2025, CDC ArboNET counted 12 human West Nile cases in Story County (6 neuroinvasive) across 8 years. The worst was 2018 with 4; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.