Mosquito season in Morton County, ND: when it starts and ends
Mosquito months in Morton County
In a normal year mosquito season in Morton County, ND starts around May 8 and ends around September 30, about 21 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Morton County, and when
- Start tipping out standing water weekly by April 24.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after September 30.
- 42 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to July, and check ND spray notices.
Morton County against the rest of ND
Morton County has the 39th longest season of 53 ND counties, at 145 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 42.5°F.
- Pierce County: May 7 to September 29 (145 days, 4 WNV)
- Benson County: May 8 to September 30 (145 days, 4 WNV)
- Pembina County: May 8 to September 29 (145 days, 2 WNV)
- Bowman County: May 9 to October 2 (145 days, 3 WNV)
West Nile in Morton County
From 1999 to 2025, CDC ArboNET counted 151 human West Nile cases in Morton County (26 neuroinvasive) across 20 years. The worst was 2003 with 48; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.