Mosquito season in Seneca County, OH: when it starts and ends
Mosquito months in Seneca County
In a normal year mosquito season in Seneca County, OH starts around April 17 and ends around October 24, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Seneca County, and when
- Start tipping out standing water weekly by April 3.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 24.
- No West Nile cases since 2016, so bites in Seneca County are a nuisance; check window screens.
Seneca County against the rest of OH
Seneca County has the 56th longest season of 88 OH counties, at 190 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 50.9°F.
- Marion County: April 16 to October 23 (190 days, 3 WNV)
- Richland County: April 16 to October 23 (190 days, 2 WNV)
- Lawrence County: April 18 to October 25 (190 days, 0 WNV)
- Wood County: April 18 to October 24 (190 days, 1 WNV)
West Nile in Seneca County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Seneca County (1 neuroinvasive) across 2 years. The worst was 2007 with 1; the latest was 2007.
More: how the dates are worked out · when mosquitoes go away for the winter.