Mosquito season in Morrison County, MN: when it starts and ends
Mosquito months in Morrison County
In a normal year mosquito season in Morrison County, MN starts around April 27 and ends around October 10, about 24 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Morrison County, and when
- Start tipping out standing water weekly by April 13.
- Book any yard treatment for late April, ahead of the July peak.
- Repellent can go away after October 10.
- 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Morrison County against the rest of MN
Morrison County has the 17th longest season of 87 MN counties, at 167 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 44.6°F.
- Sibley County: April 26 to October 11 (167 days, 6 WNV)
- Waseca County: April 26 to October 10 (167 days, 2 WNV)
- Washington County: April 27 to October 11 (167 days, 5 WNV)
- Steele County: April 28 to October 11 (167 days, 3 WNV)
West Nile in Morrison County
From 1999 to 2025, CDC ArboNET counted 5 human West Nile cases in Morrison County (2 neuroinvasive) across 4 years. The worst was 2025 with 2; the latest was 2025.
More: how the dates are worked out · when mosquitoes go away for the winter.