Mosquito season in Delaware County, OH: when it starts and ends
Mosquito months in Delaware County
In a normal year mosquito season in Delaware County, OH starts around April 9 and ends around October 28, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Delaware County, and when
- Start tipping out standing water weekly by March 26.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 28.
- No West Nile cases since 2016, so bites in Delaware County are a nuisance; check window screens.
Delaware County against the rest of OH
Delaware County has the 14th longest season of 88 OH counties, at 202 days against 209 in Gallia County and 177 in Ashtabula County. Its mean temperature is 52.9°F.
- Butler County: April 8 to October 27 (202 days, 3 WNV)
- Franklin County: April 8 to October 27 (202 days, 18 WNV)
- Pike County: April 9 to October 28 (202 days, 0 WNV)
- Clermont County: April 11 to October 27 (199 days, 6 WNV)
West Nile in Delaware County
CDC ArboNET lists no human West Nile cases for Delaware County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 21 of those years.
See how the dates are worked out, and when mosquitoes go away for the winter.