Mosquito season in Mercer County, MO: when it starts and ends
Mosquito months in Mercer County
In a normal year mosquito season in Mercer County, MO starts around April 14 and ends around October 23, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Mercer County, and when
- Start tipping out standing water weekly by March 31.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- No West Nile cases since 2016, so bites in Mercer County are a nuisance; check window screens.
Mercer County against the rest of MO
Mercer County has the 112th longest season of 115 MO counties, at 192 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 51.1°F.
- Putnam County: April 13 to October 22 (192 days, 0 WNV)
- Scotland County: April 13 to October 22 (192 days, 0 WNV)
- Sullivan County: April 14 to October 22 (191 days, 0 WNV)
- Worth County: April 14 to October 21 (190 days, 0 WNV)
West Nile in Mercer County
CDC ArboNET lists no human West Nile cases for Mercer County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 3 of those years.
Background: when mosquitoes go away for the winter; how the dates are worked out.