Mosquito season in Clinton County, IL: when it starts and ends
Mosquito months in Clinton County
In a normal year mosquito season in Clinton County, IL starts around March 30 and ends around November 3, about 31 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clinton County, and when
- Start tipping out standing water weekly by March 16.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 3.
- 2 West Nile cases since 2016 (last 2018): you should use repellent at dusk June to August, more so if over 60.
Clinton County against the rest of IL
Clinton County has the 13th longest season of 102 IL counties, at 219 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 55.7°F.
- Wabash County: March 28 to November 4 (221 days, 1 WNV)
- Perry County: March 28 to November 2 (219 days, 0 WNV)
- Monroe County: March 31 to November 4 (218 days, 1 WNV)
- Williamson County: March 29 to November 1 (217 days, 3 WNV)
West Nile in Clinton County
From 1999 to 2025, CDC ArboNET counted 12 human West Nile cases in Clinton County (8 neuroinvasive) across 4 years. The worst was 2002 with 7; the latest was 2018.
See how the dates are worked out, and when mosquitoes go away for the winter.