Mosquito season in Delta County, MI: when it starts and ends
Mosquito months in Delta County
In a normal year mosquito season in Delta County, MI starts around May 11 and ends around October 5, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Delta County, and when
- Start tipping out standing water weekly by April 27.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after October 5.
- 1 West Nile case since 2016 (last 2024): you should use repellent at dusk July, more so if over 60.
Delta County against the rest of MI
Delta County has the 69th longest season of 83 MI counties, at 147 days against 189 in Allegan County and 124 in Iron County. Its mean temperature is 42.3°F.
- Otsego County: May 9 to October 3 (147 days, 0 WNV)
- Kalkaska County: May 10 to October 4 (147 days, 0 WNV)
- Chippewa County: May 11 to October 3 (145 days, 0 WNV)
- Dickinson County: May 11 to October 3 (145 days, 0 WNV)
West Nile in Delta County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Delta County (0 neuroinvasive) across 2 years. The worst was 2024 with 1; the latest was 2024.
Background: when mosquitoes go away for the winter; how the dates are worked out.