Mosquito season in Greene County, IA: when it starts and ends
Mosquito months in Greene County
In a normal year mosquito season in Greene County, IA starts around April 20 and ends around October 17, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Greene County, and when
- Start tipping out standing water weekly by April 6.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 17.
- 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to August, more so if over 60.
Greene County against the rest of IA
Greene County has the 46th longest season of 99 IA counties, at 180 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 47.8°F.
- Story County: April 19 to October 17 (181 days, 8 WNV)
- Carroll County: April 20 to October 18 (181 days, 3 WNV)
- Monona County: April 20 to October 17 (180 days, 2 WNV)
- Marshall County: April 20 to October 16 (179 days, 1 WNV)
West Nile in Greene County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Greene County (2 neuroinvasive) across 3 years. The worst was 2025 with 1; the latest was 2025.
See how the dates are worked out, and when mosquitoes go away for the winter.