Mosquito season in Vermilion County, IL: when it starts and ends
Mosquito months in Vermilion County
In a normal year mosquito season in Vermilion County, IL starts around April 8 and ends around October 28, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Vermilion County, and when
- Start tipping out standing water weekly by March 25.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 28.
- 1 West Nile case since 2016 (last 2024): you should use repellent at dusk June to August, more so if over 60.
Vermilion County against the rest of IL
Vermilion County has the 51st longest season of 102 IL counties, at 203 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 52.8°F.
- Sangamon County: April 7 to October 28 (204 days, 8 WNV)
- Scott County: April 7 to October 27 (203 days, 1 WNV)
- Brown County: April 8 to October 27 (202 days, 0 WNV)
- Morgan County: April 8 to October 27 (202 days, 1 WNV)
West Nile in Vermilion County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Vermilion County (6 neuroinvasive) across 5 years. The worst was 2013 with 3; the latest was 2024.
See how the dates are worked out, and when mosquitoes go away for the winter.