Mosquito season in Cavalier County, ND: when it starts and ends

Mosquito months in Cavalier County

In a normal year mosquito season in Cavalier County, ND starts around May 11 and ends around September 26, about 20 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Cavalier County, and when

• Start tipping out standing water weekly by April 27.
• Book any yard treatment for mid May, ahead of the July peak.
• Repellent can go away after September 26.
• 1 West Nile case since 2016 (last 2018): you should use repellent at dusk July, more so if over 60.

Cavalier County against the rest of ND

Cavalier County has the 50th longest season of 53 ND counties, at 138 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 37.1°F.

• Mountrail County: May 11 to September 27 (139 days, 20 WNV)
• Burke County: May 10 to September 25 (138 days, 2 WNV)
• Towner County: May 12 to September 26 (137 days, 0 WNV)
• Adams County: May 13 to September 27 (137 days, 1 WNV)

West Nile in Cavalier County

From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Cavalier County (2 neuroinvasive) across 5 years. The worst was 2007 with 2; the latest was 2018.

See how the dates are worked out, and when the season starts across the US.