Mosquito season in Roseau County, MN: when it starts and ends
Mosquito months in Roseau County
In a normal year mosquito season in Roseau County, MN starts around May 10 and ends around September 28, about 20 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Roseau County, and when
- Start tipping out standing water weekly by April 26.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after September 28.
- 2 West Nile cases since 2016 (last 2021): you should use repellent at dusk July, more so if over 60.
Roseau County against the rest of MN
Roseau County has the 82nd longest season of 87 MN counties, at 141 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 38°F.
- Lake of the Woods County: May 9 to September 29 (143 days, 0 WNV)
- Itasca County: May 10 to September 29 (142 days, 5 WNV)
- Carlton County: May 12 to September 30 (141 days, 0 WNV)
- Koochiching County: May 12 to September 25 (137 days, 1 WNV)
West Nile in Roseau County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Roseau County (2 neuroinvasive) across 7 years. The worst was 2007 with 2; the latest was 2021.
Background: when mosquitoes go away for the winter; how the dates are worked out.