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

Mosquito months in Roscommon County

In a normal year mosquito season in Roscommon County, MI starts around May 4 and ends around October 5, about 22 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 Roscommon County, and when

• Start tipping out standing water weekly by April 20.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 5.
• No West Nile cases since 2016, so bites in Roscommon County are a nuisance; check window screens.

Roscommon County against the rest of MI

Roscommon County has the 57th longest season of 83 MI counties, at 154 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 44.1°F.

• Clare County: May 6 to October 8 (155 days, 0 WNV)
• Charlevoix County: May 9 to October 11 (155 days, 0 WNV)
• Presque Isle County: May 8 to October 8 (153 days, 1 WNV)
• Cheboygan County: May 9 to October 8 (152 days, 0 WNV)

West Nile in Roscommon County

CDC ArboNET lists no human West Nile cases for Roscommon County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 7 of those years.

Background: when the season starts across the US; how the dates are worked out.