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

Mosquito months in Grant County

In a normal year mosquito season in Grant County, MN starts around May 1 and ends around October 7, about 23 weeks.

What to do in Grant County, and when

Start tipping out standing water weekly by April 17.
Book any yard treatment for early May, ahead of the July peak.
Repellent can go away after October 7.
2 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.

Grant County against the rest of MN

Grant County has the 47th longest season of 87 MN counties, at 159 days against 176 in Winona County and 118 in Cook County. Its mean temperature is 42.6°F.

Kandiyohi County: April 30 to October 8 (160 days, 9 WNV)
Murray County: May 1 to October 8 (160 days, 8 WNV)
Stevens County: May 1 to October 6 (159 days, 3 WNV)
Pope County: May 1 to October 6 (158 days, 0 WNV)

West Nile in Grant County

From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Grant County (2 neuroinvasive) across 7 years. The worst was 2012 with 2; the latest was 2025.

See how the dates are worked out, and when the season starts across the US.