Mosquito season in Big Stone County, MN: when it starts and ends

Mosquito months in Big Stone County

In a normal year mosquito season in Big Stone County, MN starts around April 28 and ends around October 9, about 23 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Big Stone County, and when

• Start tipping out standing water weekly by April 14.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 9.
• 5 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to July, more so if over 60.

Big Stone County against the rest of MN

Big Stone County has the 29th longest season of 87 MN counties, at 164 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 44.1°F.

• Yellow Medicine County: April 28 to October 10 (165 days, 6 WNV)
• Anoka County: April 28 to October 9 (164 days, 23 WNV)
• Le Sueur County: April 28 to October 9 (164 days, 4 WNV)
• Olmsted County: April 28 to October 9 (164 days, 2 WNV)

West Nile in Big Stone County

From 1999 to 2025, CDC ArboNET counted 22 human West Nile cases in Big Stone County (6 neuroinvasive) across 11 years. The worst was 2007 with 8; the latest was 2023.

Background: reading the West Nile counts; how the dates are worked out.