Mosquito season in Richland County, ND: when it starts and ends
Mosquito months in Richland County
In a normal year mosquito season in Richland 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 Richland 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.
- 11 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to July, and check ND spray notices.
Richland County against the rest of ND
Richland County has the 2nd longest season of 53 ND counties, at 159 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 42.4°F.
- Sheridan County: April 30 to October 7 (160 days, 2 WNV)
- Sioux County: May 1 to October 6 (159 days, 4 WNV)
- Dickey County: April 30 to October 5 (158 days, 9 WNV)
West Nile in Richland County
From 1999 to 2025, CDC ArboNET counted 53 human West Nile cases in Richland County (16 neuroinvasive) across 16 years. The worst was 2003 with 11; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.