Mosquito season in Piatt County, IL: when it starts and ends
Mosquito months in Piatt County
In a normal year mosquito season in Piatt County, IL starts around April 11 and ends around October 23, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Piatt County, and when
- Start tipping out standing water weekly by March 28.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- No West Nile cases since 2016, so bites in Piatt County are a nuisance; check window screens.
Piatt County against the rest of IL
Piatt County has the 71st longest season of 102 IL counties, at 195 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 51.9°F.
- Putnam County: April 11 to October 25 (197 days, 0 WNV)
- Fulton County: April 11 to October 25 (196 days, 1 WNV)
- Kankakee County: April 14 to October 25 (194 days, 4 WNV)
- Ford County: April 13 to October 23 (193 days, 1 WNV)
West Nile in Piatt County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Piatt County (2 neuroinvasive) across 1 year. The worst was 2003 with 3; the latest was 2003.
See how the dates are worked out, and when the season starts across the US.