Mosquito season in Putnam County, IL: when it starts and ends
Mosquito months in Putnam County
In a normal year mosquito season in Putnam County, IL starts around April 11 and ends around October 25, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Putnam 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 25.
- No West Nile cases since 2016, so bites in Putnam County are a nuisance; check window screens.
Putnam County against the rest of IL
Putnam County has the 69th longest season of 102 IL counties, at 197 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 51.3°F.
- Edgar County: April 11 to October 25 (197 days, 2 WNV)
- Livingston County: April 11 to October 25 (197 days, 0 WNV)
- Fulton County: April 11 to October 25 (196 days, 1 WNV)
- Piatt County: April 11 to October 23 (195 days, 0 WNV)
West Nile in Putnam County
CDC ArboNET lists no human West Nile cases for Putnam County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 8 of those years.
Background: when mosquitoes go away for the winter; how the dates are worked out.