Mosquito season in Clark County, OH: when it starts and ends
Mosquito months in Clark County
In a normal year mosquito season in Clark County, OH starts around April 15 and ends around October 24, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clark 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.
- 5 West Nile cases since 2016 (last 2021): you should use repellent at dusk June to August, more so if over 60.
Clark County against the rest of OH
Clark County has the 42nd longest season of 88 OH counties, at 192 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 51.3°F.
- Champaign County: April 14 to October 23 (192 days, 0 WNV)
- Harrison County: April 14 to October 23 (192 days, 0 WNV)
- Coshocton County: April 15 to October 24 (192 days, 0 WNV)
- Fairfield County: April 15 to October 24 (192 days, 0 WNV)
West Nile in Clark County
From 1999 to 2025, CDC ArboNET counted 37 human West Nile cases in Clark County (27 neuroinvasive) across 8 years. The worst was 2002 with 14; the latest was 2021.
More: how the dates are worked out · reading the West Nile counts.