Mosquito season in Grundy County, MO: when it starts and ends
Mosquito months in Grundy County
In a normal year mosquito season in Grundy County, MO starts around April 9 and ends around October 26, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Grundy County, and when
- Start tipping out standing water weekly by March 26.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 26.
- 1 West Nile case since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Grundy County against the rest of MO
Grundy County has the 92nd longest season of 115 MO counties, at 200 days against 242 in Pemiscot County and 187 in Crawford County. Its mean temperature is 52.7°F.
- Holt County: April 8 to October 25 (200 days, 0 WNV)
- Buchanan County: April 9 to October 26 (200 days, 7 WNV)
- Monroe County: April 11 to October 28 (200 days, 0 WNV)
- Dallas County: April 9 to October 25 (199 days, 1 WNV)
West Nile in Grundy County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in Grundy County (1 neuroinvasive) across 1 year. The worst was 2025 with 1; the latest was 2025.
See how the dates are worked out, and when the season starts across the US.