Mosquito season in Sac County, IA: when it starts and ends
Mosquito months in Sac County
In a normal year mosquito season in Sac County, IA starts around April 23 and ends around October 14, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Sac 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 14.
- No West Nile cases since 2016, so bites in Sac County are a nuisance; check window screens.
Sac County against the rest of IA
Sac County has the 76th longest season of 99 IA counties, at 174 days against 198 in Des Moines County and 160 in Worth County. Its mean temperature is 46.8°F.
- Bremer County: April 23 to October 14 (174 days, 4 WNV)
- Franklin County: April 23 to October 15 (174 days, 1 WNV)
- Cass County: April 22 to October 12 (173 days, 0 WNV)
- Clay County: April 23 to October 13 (173 days, 0 WNV)
West Nile in Sac County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Sac County (2 neuroinvasive) across 3 years. The worst was 2005 with 2; the latest was 2014.
More: how the dates are worked out · when the season starts across the US.