Mosquito season in St. Joseph County, IN: when it starts and ends
Mosquito months in St. Joseph County
In a normal year mosquito season in St. Joseph County, IN starts around April 21 and ends around October 20, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in St. Joseph County, and when
- Start tipping out standing water weekly by April 7.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 20.
- 2 West Nile cases since 2016 (last 2021): you should use repellent at dusk July to August, more so if over 60.
St. Joseph County against the rest of IN
St. Joseph County has the 90th longest season of 92 IN counties, at 182 days against 231 in Floyd County and 177 in Steuben County. Its mean temperature is 49.1°F.
- LaGrange County: April 19 to October 20 (184 days, 0 WNV)
- Huntington County: April 20 to October 21 (184 days, 1 WNV)
- DeKalb County: April 22 to October 19 (180 days, 0 WNV)
- Steuben County: April 23 to October 17 (177 days, 0 WNV)
West Nile in St. Joseph County
From 1999 to 2025, CDC ArboNET counted 13 human West Nile cases in St. Joseph County (4 neuroinvasive) across 6 years. The worst was 2002 with 5; the latest was 2021.
Background: when mosquitoes go away for the winter; how the dates are worked out.