Mosquito season in Jefferson County, OH: when it starts and ends
Mosquito months in Jefferson County
In a normal year mosquito season in Jefferson County, OH starts around April 18 and ends around October 24, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Jefferson County, and when
- Start tipping out standing water weekly by April 4.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 24.
- 1 West Nile case since 2016 (last 2021): you should use repellent at dusk July to August, more so if over 60.
Jefferson County against the rest of OH
Jefferson County has the 59th longest season of 88 OH counties, at 189 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 51.2°F.
- Lawrence County: April 18 to October 25 (190 days, 0 WNV)
- Wood County: April 18 to October 24 (190 days, 1 WNV)
- Sandusky County: April 18 to October 24 (189 days, 1 WNV)
- Noble County: April 19 to October 25 (189 days, 1 WNV)
West Nile in Jefferson County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Jefferson County (1 neuroinvasive) across 1 year. The worst was 2021 with 1; the latest was 2021.
More: how the dates are worked out · when the season starts across the US.