Mosquito season in Shiawassee County, MI: when it starts and ends
Mosquito months in Shiawassee County
In a normal year mosquito season in Shiawassee County, MI starts around April 27 and ends around October 16, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Shiawassee 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 16.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July to July, more so if over 60.
Shiawassee County against the rest of MI
Shiawassee County has the 24th longest season of 83 MI counties, at 173 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 47.7°F.
- Kent County: April 27 to October 17 (173 days, 46 WNV)
- Lapeer County: April 27 to October 17 (173 days, 2 WNV)
- Eaton County: April 26 to October 15 (172 days, 2 WNV)
- Livingston County: April 26 to October 15 (172 days, 3 WNV)
West Nile in Shiawassee County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Shiawassee County (2 neuroinvasive) across 2 years. The worst was 2023 with 1; the latest was 2023.
Background: when the season starts across the US; how the dates are worked out.