Mosquito season in Whiteside County, IL: when it starts and ends
Mosquito months in Whiteside County
In a normal year mosquito season in Whiteside County, IL starts around April 19 and ends around October 18, about 26 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Whiteside County, and when
- Start tipping out standing water weekly by April 5.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 18.
- 1 West Nile case since 2016 (last 2018): you should use repellent at dusk July to August, more so if over 60.
Whiteside County against the rest of IL
Whiteside County has the 96th longest season of 102 IL counties, at 181 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 48.5°F.
- Lee County: April 20 to October 19 (182 days, 2 WNV)
- McHenry County: April 21 to October 19 (182 days, 11 WNV)
- DeKalb County: April 20 to October 18 (180 days, 6 WNV)
- Jo Daviess County: April 22 to October 16 (177 days, 1 WNV)
West Nile in Whiteside County
From 1999 to 2025, CDC ArboNET counted 7 human West Nile cases in Whiteside County (3 neuroinvasive) across 5 years. The worst was 2003 with 3; the latest was 2018.
Background: when the season starts across the US; how the dates are worked out.