Mosquito season in Madison County, MO: when it starts and ends

Mosquito months in Madison County

In a normal year mosquito season in Madison County, MO starts around April 10 and ends around October 26, about 28 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Madison County, and when

• Start tipping out standing water weekly by March 27.
• Book any yard treatment for early April, ahead of the July peak.
• Repellent can go away after October 26.
• No West Nile cases since 2016, so bites in Madison County are a nuisance; check window screens.

Madison County against the rest of MO

Madison County has the 97th longest season of 115 MO counties, at 199 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 55.1°F.

• Knox County: April 9 to October 25 (199 days, 0 WNV)
• Clinton County: April 10 to October 26 (199 days, 1 WNV)
• Shelby County: April 11 to October 27 (199 days, 0 WNV)
• Gentry County: April 11 to October 25 (198 days, 0 WNV)

West Nile in Madison County

CDC ArboNET lists no human West Nile cases for Madison County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 2 of those years.

Background: when the season starts across the US; how the dates are worked out.