Mosquito season in Massac County, IL: when it starts and ends
Mosquito months in Massac County
In a normal year mosquito season in Massac County, IL starts around March 27 and ends around November 5, about 32 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Massac County, and when
- Start tipping out standing water weekly by March 13.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 5.
- 4 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to September, more so if over 60.
Massac County against the rest of IL
Massac County has the 8th 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.
- Alexander County: March 26 to November 4 (223 days, 0 WNV)
- Edwards County: March 27 to November 5 (223 days, 1 WNV)
- Wayne County: March 27 to November 5 (223 days, 1 WNV)
- Franklin County: March 27 to November 4 (222 days, 8 WNV)
West Nile in Massac County
From 1999 to 2025, CDC ArboNET counted 4 human West Nile cases in Massac County (2 neuroinvasive) across 4 years. The worst was 2025 with 1; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.