Mosquito season in Clay County, MO: when it starts and ends
Mosquito months in Clay County
In a normal year mosquito season in Clay County, MO starts around April 8 and ends around October 27, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Clay County, and when
- Start tipping out standing water weekly by March 25.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 27.
- 4 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Clay County against the rest of MO
Clay County has the 84th longest season of 115 MO counties, at 202 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 53.5°F.
- Shannon County: April 6 to October 28 (205 days, 1 WNV)
- Ralls County: April 7 to October 28 (204 days, 0 WNV)
- Lewis County: April 8 to October 27 (202 days, 0 WNV)
- Linn County: April 7 to October 25 (201 days, 0 WNV)
West Nile in Clay County
From 1999 to 2025, CDC ArboNET counted 18 human West Nile cases in Clay County (15 neuroinvasive) across 11 years. The worst was 2015 with 3; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.