Mosquito season in Polk County, MN: when it starts and ends
Mosquito months in Polk County
In a normal year mosquito season in Polk County, MN starts around May 5 and ends around October 2, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Polk County, and when
- Start tipping out standing water weekly by April 21.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 2.
- 15 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July, and check MN spray notices.
Polk County against the rest of MN
Polk County has the 70th longest season of 87 MN counties, at 149 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 39.9°F.
- Marshall County: May 5 to October 1 (149 days, 4 WNV)
- Pennington County: May 5 to October 1 (149 days, 0 WNV)
- Red Lake County: May 5 to October 2 (149 days, 1 WNV)
- Hubbard County: May 6 to October 1 (148 days, 0 WNV)
West Nile in Polk County
From 1999 to 2025, CDC ArboNET counted 35 human West Nile cases in Polk County (15 neuroinvasive) across 15 years. The worst was 2007 with 8; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.