Mosquito season in Shelby County, MO: when it starts and ends
Mosquito months in Shelby County
In a normal year mosquito season in Shelby County, MO starts around April 11 and ends around October 27, about 28 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Shelby 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 27.
- No West Nile cases since 2016, so bites in Shelby County are a nuisance; check window screens.
Shelby County against the rest of MO
Shelby County has the 98th longest season of 115 MO counties, at 199 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 52.6°F.
- Clinton County: April 10 to October 26 (199 days, 1 WNV)
- Madison County: April 10 to October 26 (199 days, 0 WNV)
- Gentry County: April 11 to October 25 (198 days, 0 WNV)
- Daviess County: April 10 to October 24 (197 days, 0 WNV)
West Nile in Shelby County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Shelby County (0 neuroinvasive) across 1 year. The worst was 2003 with 1; the latest was 2003.
Background: when the season starts across the US; how the dates are worked out.