Mosquito season in Richland County, IL: when it starts and ends
Mosquito months in Richland County
In a normal year mosquito season in Richland County, IL starts around April 3 and ends around October 31, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Richland County, and when
- Start tipping out standing water weekly by March 20.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 31.
- 1 West Nile case since 2016 (last 2016): you should use repellent at dusk June to August, more so if over 60.
Richland County against the rest of IL
Richland County has the 34th longest season of 102 IL counties, at 210 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 54.2°F.
- Jasper County: April 3 to October 31 (211 days, 0 WNV)
- Fayette County: April 2 to October 30 (210 days, 0 WNV)
- Crawford County: April 4 to October 30 (209 days, 0 WNV)
- White County: April 3 to October 28 (208 days, 0 WNV)
West Nile in Richland County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Richland County (3 neuroinvasive) across 3 years. The worst was 2016 with 1; the latest was 2016.
More: how the dates are worked out · when mosquitoes go away for the winter.