Mosquito season in Washington County, IN: when it starts and ends
Mosquito months in Washington County
In a normal year mosquito season in Washington County, IN starts around April 4 and ends around November 1, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Washington County, and when
- Start tipping out standing water weekly by March 21.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after November 1.
- No West Nile cases since 2016, so bites in Washington County are a nuisance; check window screens.
Washington County against the rest of IN
Washington County has the 19th longest season of 92 IN counties, at 211 days against 231 in Floyd County and 177 in Steuben County. Its mean temperature is 55.4°F.
- Switzerland County: April 4 to November 2 (212 days, 0 WNV)
- Crawford County: April 3 to October 31 (211 days, 1 WNV)
- Harrison County: April 6 to November 2 (210 days, 0 WNV)
- Clay County: April 3 to October 29 (209 days, 1 WNV)
West Nile in Washington County
CDC ArboNET lists no human West Nile cases for Washington County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 17 of those years.
Background: when the season starts across the US; how the dates are worked out.