Mosquito season in Warren County, OH: when it starts and ends
Mosquito months in Warren County
In a normal year mosquito season in Warren County, OH starts around April 6 and ends around October 29, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Warren County, and when
- Start tipping out standing water weekly by March 23.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 29.
- 3 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Warren County against the rest of OH
Warren County has the 9th longest season of 88 OH counties, at 206 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 53.5°F.
- Montgomery County: April 6 to October 29 (206 days, 14 WNV)
- Ross County: April 6 to October 29 (206 days, 3 WNV)
- Clinton County: April 6 to October 28 (205 days, 0 WNV)
- Miami County: April 8 to October 28 (203 days, 1 WNV)
West Nile in Warren County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Warren County (8 neuroinvasive) across 5 years. The worst was 2002 with 3; the latest was 2025.
Background: when mosquitoes go away for the winter; how the dates are worked out.