Mosquito season in Shelby County, IN: when it starts and ends
Mosquito months in Shelby County
In a normal year mosquito season in Shelby County, IN starts around April 8 and ends around October 28, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Shelby 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 28.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Shelby County against the rest of IN
Shelby County has the 35th longest season of 92 IN counties, at 203 days against 231 in Floyd County and 177 in Steuben County. Its mean temperature is 52.7°F.
- Orange County: April 8 to October 29 (204 days, 1 WNV)
- Owen County: April 7 to October 27 (203 days, 0 WNV)
- Ohio County: April 11 to October 31 (203 days, 1 WNV)
- Marion County: April 8 to October 27 (202 days, 18 WNV)
West Nile in Shelby County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Shelby County (1 neuroinvasive) across 1 year. The worst was 2025 with 1; the latest was 2025.
Background: when mosquitoes go away for the winter; how the dates are worked out.