Mosquito season in Koochiching County, MN: when it starts and ends
Mosquito months in Koochiching County
In a normal year mosquito season in Koochiching County, MN starts around May 12 and ends around September 25, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Koochiching County, and when
- Start tipping out standing water weekly by April 28.
- Book any yard treatment for mid May, ahead of the July peak.
- Repellent can go away after September 25.
- 1 West Nile case since 2016 (last 2022): you should use repellent at dusk July, more so if over 60.
Koochiching County against the rest of MN
Koochiching County has the 84th longest season of 87 MN counties, at 137 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 37.5°F.
- Roseau County: May 10 to September 28 (141 days, 2 WNV)
- Carlton County: May 12 to September 30 (141 days, 0 WNV)
- St. Louis County: May 13 to September 26 (136 days, 7 WNV)
- Lake County: May 16 to September 25 (132 days, 1 WNV)
West Nile in Koochiching County
From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Koochiching County (2 neuroinvasive) across 2 years. The worst was 2022 with 1; the latest was 2022.
More: how the dates are worked out · when the season starts across the US.