Mosquito season in Ottawa County, OH: when it starts and ends
Mosquito months in Ottawa County
In a normal year mosquito season in Ottawa County, OH starts around April 17 and ends around October 26, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Ottawa 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 26.
- 1 West Nile case since 2016 (last 2023): you should use repellent at dusk June to August, more so if over 60.
Ottawa County against the rest of OH
Ottawa County has the 52nd longest season of 88 OH counties, at 191 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 51.2°F.
- Hardin County: April 16 to October 24 (191 days, 2 WNV)
- Shelby County: April 16 to October 24 (191 days, 0 WNV)
- Logan County: April 16 to October 23 (190 days, 2 WNV)
- Marion County: April 16 to October 23 (190 days, 3 WNV)
West Nile in Ottawa County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Ottawa County (2 neuroinvasive) across 3 years. The worst was 2002 with 2; the latest was 2023.
See how the dates are worked out, and when the season starts across the US.