Mosquito season in Brown County, IL: when it starts and ends
Mosquito months in Brown County
In a normal year mosquito season in Brown County, IL starts around April 8 and ends around October 27, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Brown 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 27.
- No West Nile cases since 2016, so bites in Brown County are a nuisance; check window screens.
Brown County against the rest of IL
Brown County has the 52nd longest season of 102 IL counties, at 202 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 52.5°F.
- Scott County: April 7 to October 27 (203 days, 1 WNV)
- Vermilion County: April 8 to October 28 (203 days, 1 WNV)
- Morgan County: April 8 to October 27 (202 days, 1 WNV)
- Cass County: April 8 to October 27 (201 days, 0 WNV)
West Nile in Brown County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Brown County (1 neuroinvasive) across 1 year. The worst was 2006 with 1; the latest was 2006.
More: how the dates are worked out · when the season starts across the US.