Mosquito season in Warren County, IL: when it starts and ends
Mosquito months in Warren County
In a normal year mosquito season in Warren County, IL starts around April 13 and ends around October 22, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Warren County, and when
- Start tipping out standing water weekly by March 30.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 22.
- 1 West Nile case since 2016 (last 2016): you should use repellent at dusk June to August, more so if over 60.
Warren County against the rest of IL
Warren County has the 78th longest season of 102 IL counties, at 192 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 50.3°F.
- Iroquois County: April 14 to October 24 (193 days, 0 WNV)
- Woodford County: April 15 to October 25 (193 days, 3 WNV)
- McLean County: April 14 to October 23 (192 days, 4 WNV)
- Grundy County: April 15 to October 23 (192 days, 2 WNV)
West Nile in Warren County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Warren County (2 neuroinvasive) across 3 years. The worst was 2016 with 1; the latest was 2016.
See how the dates are worked out, and when mosquitoes go away for the winter.