Mosquito season in Ottawa County, MI: when it starts and ends
Mosquito months in Ottawa County
In a normal year mosquito season in Ottawa County, MI starts around April 27 and ends around October 19, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Ottawa County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 19.
- 6 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Ottawa County against the rest of MI
Ottawa County has the 21st longest season of 83 MI counties, at 174 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 48.3°F.
- Saginaw County: April 25 to October 17 (174 days, 1 WNV)
- St. Clair County: April 26 to October 17 (174 days, 6 WNV)
- Kent County: April 27 to October 17 (173 days, 46 WNV)
- Lapeer County: April 27 to October 17 (173 days, 2 WNV)
West Nile in Ottawa County
From 1999 to 2025, CDC ArboNET counted 25 human West Nile cases in Ottawa County (19 neuroinvasive) across 10 years. The worst was 2002 with 12; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.