Mosquito season in Butler County, OH: when it starts and ends
Mosquito months in Butler County
In a normal year mosquito season in Butler County, OH starts around April 8 and ends around October 27, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Butler County, and when
- Start tipping out standing water weekly by March 25.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 27.
- 3 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Butler County against the rest of OH
Butler County has the 12th longest season of 88 OH counties, at 202 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 53.6°F.
- Clinton County: April 6 to October 28 (205 days, 0 WNV)
- Miami County: April 8 to October 28 (203 days, 1 WNV)
- Franklin County: April 8 to October 27 (202 days, 18 WNV)
- Delaware County: April 9 to October 28 (202 days, 0 WNV)
West Nile in Butler County
From 1999 to 2025, CDC ArboNET counted 21 human West Nile cases in Butler County (19 neuroinvasive) across 11 years. The worst was 2012 with 5; the latest was 2025.
More: how the dates are worked out · when the season starts across the US.