Mosquito season in Grand Forks County, ND: when it starts and ends
Mosquito months in Grand Forks County
In a normal year mosquito season in Grand Forks County, ND starts around May 6 and ends around October 1, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Grand Forks County, and when
- Start tipping out standing water weekly by April 22.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 1.
- 17 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July, and check ND spray notices.
Grand Forks County against the rest of ND
Grand Forks County has the 24th longest season of 53 ND counties, at 149 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 39.9°F.
- Barnes County: May 6 to October 2 (149 days, 15 WNV)
- Eddy County: May 6 to October 1 (149 days, 0 WNV)
- Kidder County: May 6 to October 2 (149 days, 2 WNV)
- Logan County: May 6 to October 2 (149 days, 0 WNV)
West Nile in Grand Forks County
From 1999 to 2025, CDC ArboNET counted 36 human West Nile cases in Grand Forks County (12 neuroinvasive) across 16 years. The worst was 2018 with 6; the latest was 2025.
Background: reading the West Nile counts; how the dates are worked out.