Mosquito season in McLean County, IL: when it starts and ends
Mosquito months in McLean County
In a normal year mosquito season in McLean County, IL starts around April 14 and ends around October 23, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in McLean County, and when
- Start tipping out standing water weekly by March 31.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- 4 West Nile cases since 2016 (last 2022): you should use repellent at dusk June to August, more so if over 60.
McLean County against the rest of IL
McLean County has the 79th longest season of 102 IL counties, at 192 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 50.9°F.
- Woodford County: April 15 to October 25 (193 days, 3 WNV)
- Warren County: April 13 to October 22 (192 days, 1 WNV)
- Grundy County: April 15 to October 23 (192 days, 2 WNV)
- Henry County: April 14 to October 22 (191 days, 0 WNV)
West Nile in McLean County
From 1999 to 2025, CDC ArboNET counted 20 human West Nile cases in McLean County (14 neuroinvasive) across 10 years. The worst was 2005 with 4; the latest was 2022.
See how the dates are worked out, and reading the West Nile counts.