Mosquito season in Jackson County, IL: when it starts and ends
Mosquito months in Jackson County
In a normal year mosquito season in Jackson County, IL starts around March 30 and ends around November 1, about 31 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Jackson 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 1.
- 3 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Jackson County against the rest of IL
Jackson County has the 16th longest season of 102 IL counties, at 216 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 56.3°F.
- Monroe County: March 31 to November 4 (218 days, 1 WNV)
- Williamson County: March 29 to November 1 (217 days, 3 WNV)
- Clay County: March 31 to November 2 (216 days, 0 WNV)
- Washington County: March 31 to November 2 (216 days, 0 WNV)
West Nile in Jackson County
From 1999 to 2025, CDC ArboNET counted 13 human West Nile cases in Jackson County (6 neuroinvasive) across 6 years. The worst was 2002 with 6; the latest was 2025.
See how the dates are worked out, and when mosquitoes go away for the winter.