Mosquito season in St. Francois County, MO: when it starts and ends
Mosquito months in St. Francois County
In a normal year mosquito season in St. Francois County, MO starts around April 1 and ends around November 1, about 31 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in St. Francois County, and when
- Start tipping out standing water weekly by March 18.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after November 1.
- 1 West Nile case since 2016 (last 2024): you should use repellent at dusk June to August, more so if over 60.
St. Francois County against the rest of MO
St. Francois County has the 48th longest season of 115 MO counties, at 214 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 55.9°F.
- Moniteau County: April 1 to November 1 (214 days, 0 WNV)
- Polk County: April 1 to November 1 (214 days, 0 WNV)
- Cooper County: April 1 to November 1 (213 days, 0 WNV)
- Jackson County: April 1 to October 31 (213 days, 21 WNV)
West Nile in St. Francois County
From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in St. Francois County (3 neuroinvasive) across 2 years. The worst was 2002 with 2; the latest was 2024.
See how the dates are worked out, and when the season starts across the US.