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

Mosquito months in Darke County

In a normal year mosquito season in Darke County, OH starts around April 11 and ends around October 25, about 28 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 Darke County, and when

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

Darke County against the rest of OH

Darke County has the 21st longest season of 88 OH counties, at 198 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 51.9°F.

• Union County: April 10 to October 26 (198 days, 0 WNV)
• Athens County: April 11 to October 26 (198 days, 1 WNV)
• Highland County: April 12 to October 27 (198 days, 1 WNV)
• Muskingum County: April 13 to October 28 (198 days, 0 WNV)

West Nile in Darke County

From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Darke County (6 neuroinvasive) across 6 years. The worst was 2003 with 3; the latest was 2025.

Background: when mosquitoes go away for the winter; how the dates are worked out.