Mosquito season in Richland County, OH: when it starts and ends
Mosquito months in Richland County
In a normal year mosquito season in Richland County, OH starts around April 16 and ends around October 23, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Richland County, and when
- Start tipping out standing water weekly by April 2.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- 2 West Nile cases since 2016 (last 2021): you should use repellent at dusk July to August, more so if over 60.
Richland County against the rest of OH
Richland County has the 55th longest season of 88 OH counties, at 190 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 50.4°F.
- Logan County: April 16 to October 23 (190 days, 2 WNV)
- Marion County: April 16 to October 23 (190 days, 3 WNV)
- Seneca County: April 17 to October 24 (190 days, 0 WNV)
- Lawrence County: April 18 to October 25 (190 days, 0 WNV)
West Nile in Richland County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Richland County (4 neuroinvasive) across 4 years. The worst was 2021 with 1; the latest was 2021.
See how the dates are worked out, and when mosquitoes go away for the winter.