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

Mosquito months in Carlton County

In a normal year mosquito season in Carlton County, MN starts around May 12 and ends around September 30, about 20 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 Carlton County, and when

• Start tipping out standing water weekly by April 28.
• Book any yard treatment for mid May, ahead of the July peak.
• Repellent can go away after September 30.
• No West Nile cases since 2016, so bites in Carlton County are a nuisance; check window screens.

Carlton County against the rest of MN

Carlton County has the 83rd longest season of 87 MN counties, at 141 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 39.7°F.

• Itasca County: May 10 to September 29 (142 days, 5 WNV)
• Roseau County: May 10 to September 28 (141 days, 2 WNV)
• Koochiching County: May 12 to September 25 (137 days, 1 WNV)
• St. Louis County: May 13 to September 26 (136 days, 7 WNV)

West Nile in Carlton County

CDC ArboNET lists no human West Nile cases for Carlton County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 2 of those years.

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