Mosquito season in Hillsdale County, MI: when it starts and ends
Mosquito months in Hillsdale County
In a normal year mosquito season in Hillsdale County, MI starts around April 24 and ends around October 16, about 25 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Hillsdale County, and when
- Start tipping out standing water weekly by April 10.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 16.
- 2 West Nile cases since 2016 (last 2017): you should use repellent at dusk July to July, more so if over 60.
Hillsdale County against the rest of MI
Hillsdale County has the 17th longest season of 83 MI counties, at 175 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 47.9°F.
- Oakland County: April 24 to October 17 (176 days, 62 WNV)
- Macomb County: April 26 to October 19 (176 days, 50 WNV)
- Barry County: April 25 to October 16 (174 days, 2 WNV)
- Saginaw County: April 25 to October 17 (174 days, 1 WNV)
West Nile in Hillsdale County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Hillsdale County (3 neuroinvasive) across 2 years. The worst was 2017 with 2; the latest was 2017.
See how the dates are worked out, and when mosquitoes go away for the winter.