Mosquito season in Guthrie County, IA: when it starts and ends
Mosquito months in Guthrie County
In a normal year mosquito season in Guthrie County, IA starts around April 23 and ends around October 15, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Guthrie County, and when
- Start tipping out standing water weekly by April 9.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 15.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Guthrie County against the rest of IA
Guthrie County has the 70th longest season of 99 IA counties, at 175 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 48.4°F.
- Buchanan County: April 22 to October 15 (175 days, 0 WNV)
- Plymouth County: April 22 to October 14 (175 days, 10 WNV)
- Hardin County: April 23 to October 15 (175 days, 2 WNV)
- Humboldt County: April 23 to October 15 (175 days, 3 WNV)
West Nile in Guthrie County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Guthrie County (1 neuroinvasive) across 2 years. The worst was 2025 with 1; the latest was 2025.
Background: when mosquitoes go away for the winter; how the dates are worked out.