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

Mosquito months in Freeborn County

In a normal year mosquito season in Freeborn County, MN starts around April 26 and ends around October 11, about 24 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 Freeborn County, and when

• Start tipping out standing water weekly by April 12.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 11.
• 1 West Nile case since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.

Freeborn County against the rest of MN

Freeborn County has the 13th longest season of 87 MN counties, at 167 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 45°F.

• Houston County: April 27 to October 12 (168 days, 1 WNV)
• Dakota County: April 26 to October 11 (167 days, 26 WNV)
• Nicollet County: April 26 to October 11 (167 days, 2 WNV)
• Sibley County: April 26 to October 11 (167 days, 6 WNV)

West Nile in Freeborn County

From 1999 to 2025, CDC ArboNET counted 3 human West Nile cases in Freeborn County (3 neuroinvasive) across 3 years. The worst was 2025 with 1; the latest was 2025.

Background: when mosquitoes go away for the winter; how the dates are worked out.