Mosquito season in Miami County, OH: when it starts and ends

Mosquito months in Miami County

In a normal year mosquito season in Miami County, OH starts around April 8 and ends around October 28, about 29 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 Miami County, and when

• Start tipping out standing water weekly by March 25.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after October 28.
• 1 West Nile case since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.

Miami County against the rest of OH

Miami County has the 11th longest season of 88 OH counties, at 203 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 52.8°F.

• Warren County: April 6 to October 29 (206 days, 3 WNV)
• Clinton County: April 6 to October 28 (205 days, 0 WNV)
• Butler County: April 8 to October 27 (202 days, 3 WNV)
• Franklin County: April 8 to October 27 (202 days, 18 WNV)

West Nile in Miami County

From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Miami County (5 neuroinvasive) across 5 years. The worst was 2002 with 2; the latest was 2025.

See how the dates are worked out, and when mosquitoes go away for the winter.