Mosquito season in Otsego County, MI: when it starts and ends

Mosquito months in Otsego County

In a normal year mosquito season in Otsego County, MI starts around May 9 and ends around October 3, about 21 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Otsego County, and when

• Start tipping out standing water weekly by April 25.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 3.
• No West Nile cases since 2016, so bites in Otsego County are a nuisance; check window screens.

Otsego County against the rest of MI

Otsego County has the 67th longest season of 83 MI counties, at 147 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 42.2°F.

• Crawford County: May 10 to October 5 (148 days, 0 WNV)
• Missaukee County: May 10 to October 5 (148 days, 0 WNV)
• Kalkaska County: May 10 to October 4 (147 days, 0 WNV)
• Delta County: May 11 to October 5 (147 days, 1 WNV)

West Nile in Otsego County

From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Otsego County (1 neuroinvasive) across 1 year. The worst was 2002 with 1; the latest was 2002.

See how the dates are worked out, and when the season starts across the US.