Mosquito season in Perry County, IL: when it starts and ends
Mosquito months in Perry County
In a normal year mosquito season in Perry County, IL starts around March 28 and ends around November 2, about 31 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Perry County, and when
- Start tipping out standing water weekly by March 14.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 2.
- No West Nile cases since 2016, so bites in Perry County are a nuisance; check window screens.
Perry County against the rest of IL
Perry County has the 12th longest season of 102 IL counties, at 219 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 55.6°F.
- Franklin County: March 27 to November 4 (222 days, 8 WNV)
- Wabash County: March 28 to November 4 (221 days, 1 WNV)
- Clinton County: March 30 to November 3 (219 days, 2 WNV)
- Monroe County: March 31 to November 4 (218 days, 1 WNV)
West Nile in Perry County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Perry County (1 neuroinvasive) across 1 year. The worst was 2013 with 1; the latest was 2013.
More: how the dates are worked out · when the season starts across the US.