Mosquito season in Ontonagon County, MI: when it starts and ends
Mosquito months in Ontonagon County
In a normal year mosquito season in Ontonagon County, MI starts around May 10 and ends around October 7, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Ontonagon County, and when
- Start tipping out standing water weekly by April 26.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 7.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July, more so if over 60.
Ontonagon County against the rest of MI
Ontonagon County has the 62nd longest season of 83 MI counties, at 150 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 43°F.
- Alpena County: May 10 to October 8 (151 days, 0 WNV)
- Montmorency County: May 8 to October 5 (150 days, 0 WNV)
- Emmet County: May 10 to October 7 (149 days, 2 WNV)
- Menominee County: May 10 to October 6 (149 days, 1 WNV)
West Nile in Ontonagon County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Ontonagon County (1 neuroinvasive) across 1 year. The worst was 2023 with 1; the latest was 2023.
See how the dates are worked out, and when the season starts across the US.