Mosquito season in Alexander County, IL: when it starts and ends
Mosquito months in Alexander County
In a normal year mosquito season in Alexander County, IL starts around March 26 and ends around November 4, about 32 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Alexander County, and when
- Start tipping out standing water weekly by March 12.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 4.
- No West Nile cases since 2016, so bites in Alexander County are a nuisance; check window screens.
Alexander County against the rest of IL
Alexander County has the 6th longest season of 102 IL counties, at 223 days against 232 in Pulaski County and 174 in Boone County. Its mean temperature is 57.9°F.
- Madison County: March 27 to November 6 (224 days, 9 WNV)
- Union County: March 29 to November 8 (224 days, 0 WNV)
- Edwards County: March 27 to November 5 (223 days, 1 WNV)
- Massac County: March 27 to November 5 (223 days, 4 WNV)
West Nile in Alexander County
CDC ArboNET lists no human West Nile cases for Alexander County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 3 of those years.
Background: when the season starts across the US; how the dates are worked out.