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

Mosquito months in Swift County

In a normal year mosquito season in Swift 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 Swift 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.
• 2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.

Swift County against the rest of MN

Swift County has the 33rd longest season of 87 MN counties, at 164 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 43.9°F.

• Olmsted County: April 28 to October 9 (164 days, 2 WNV)
• Pipestone County: April 28 to October 9 (164 days, 4 WNV)
• Wright County: April 28 to October 9 (164 days, 7 WNV)
• Carver County: April 29 to October 10 (164 days, 11 WNV)

West Nile in Swift County

From 1999 to 2025, CDC ArboNET counted 8 human West Nile cases in Swift County (3 neuroinvasive) across 7 years. The worst was 2012 with 2; the latest was 2025.

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