Mosquito season in Henry County, MO: when it starts and ends
Mosquito months in Henry County
In a normal year mosquito season in Henry County, MO starts around April 5 and ends around October 31, about 30 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Henry County, and when
- Start tipping out standing water weekly by March 22.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 31.
- 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Henry County against the rest of MO
Henry County has the 70th longest season of 115 MO counties, at 209 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 55.3°F.
- Chariton County: April 4 to October 30 (209 days, 0 WNV)
- Laclede County: April 4 to October 30 (209 days, 4 WNV)
- Carroll County: April 4 to October 29 (208 days, 0 WNV)
- Lafayette County: April 4 to October 29 (208 days, 0 WNV)
West Nile in Henry County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Henry County (1 neuroinvasive) across 2 years. The worst was 2025 with 1; the latest was 2025.
More: how the dates are worked out · when mosquitoes go away for the winter.