Mosquito season in Putnam County, OH: when it starts and ends
Mosquito months in Putnam County
In a normal year mosquito season in Putnam County, OH starts around April 15 and ends around October 24, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Putnam County, and when
- Start tipping out standing water weekly by April 1.
- 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 2025): you should use repellent at dusk June to August, more so if over 60.
Putnam County against the rest of OH
Putnam County has the 38th longest season of 88 OH counties, at 193 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 51.1°F.
- Allen County: April 15 to October 25 (193 days, 1 WNV)
- Mercer County: April 15 to October 25 (193 days, 2 WNV)
- Lorain County: April 16 to October 26 (193 days, 3 WNV)
- Champaign County: April 14 to October 23 (192 days, 0 WNV)
West Nile in Putnam County
From 1999 to 2025, CDC ArboNET counted 16 human West Nile cases in Putnam County (9 neuroinvasive) across 6 years. The worst was 2002 with 6; the latest was 2025.
Background: when mosquitoes go away for the winter; how the dates are worked out.