Mosquito season in Walsh County, ND: when it starts and ends
Mosquito months in Walsh County
In a normal year mosquito season in Walsh County, ND starts around May 2 and ends around October 4, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Walsh County, and when
- Start tipping out standing water weekly by April 18.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 4.
- 5 West Nile cases since 2016 (last 2025): you should use repellent at dusk July to July, more so if over 60.
Walsh County against the rest of ND
Walsh County has the 7th longest season of 53 ND counties, at 154 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 40.9°F.
- Traill County: May 2 to October 5 (157 days, 5 WNV)
- LaMoure County: May 2 to October 5 (156 days, 6 WNV)
- Cass County: May 3 to October 4 (154 days, 79 WNV)
- Emmons County: May 3 to October 4 (154 days, 4 WNV)
West Nile in Walsh County
From 1999 to 2025, CDC ArboNET counted 26 human West Nile cases in Walsh County (10 neuroinvasive) across 11 years. The worst was 2003 with 7; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.