Mosquito season in Isabella County, MI: when it starts and ends
Mosquito months in Isabella County
In a normal year mosquito season in Isabella County, MI starts around April 27 and ends around October 15, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Isabella 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 15.
- 2 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to July, more so if over 60.
Isabella County against the rest of MI
Isabella County has the 29th longest season of 83 MI counties, at 171 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 47.5°F.
- Washtenaw County: April 27 to October 16 (172 days, 3 WNV)
- Genesee County: April 27 to October 15 (171 days, 9 WNV)
- Midland County: April 27 to October 15 (171 days, 0 WNV)
- Bay County: April 28 to October 16 (171 days, 4 WNV)
West Nile in Isabella County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Isabella County (2 neuroinvasive) across 4 years. The worst was 2023 with 1; the latest was 2023.
More: how the dates are worked out · when the season starts across the US.