Mosquito season in Sioux County, ND: when it starts and ends
Mosquito months in Sioux County
In a normal year mosquito season in Sioux County, ND starts around May 1 and ends around October 6, about 23 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Sioux 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 6.
- 4 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
Sioux County against the rest of ND
Sioux County has the 3rd longest season of 53 ND counties, at 159 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 44°F.
- Sheridan County: April 30 to October 7 (160 days, 2 WNV)
- Richland County: May 1 to October 6 (159 days, 11 WNV)
- Dickey County: April 30 to October 5 (158 days, 9 WNV)
- Traill County: May 2 to October 5 (157 days, 5 WNV)
West Nile in Sioux County
From 1999 to 2025, CDC ArboNET counted 18 human West Nile cases in Sioux County (6 neuroinvasive) across 7 years. The worst was 2003 with 6; the latest was 2023.
See how the dates are worked out, and reading the West Nile counts.