Mosquito season in McHenry County, ND: when it starts and ends
Mosquito months in McHenry County
In a normal year mosquito season in McHenry County, ND starts around May 4 and ends around October 2, about 22 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in McHenry County, and when
- Start tipping out standing water weekly by April 20.
- Book any yard treatment for early May, ahead of the July peak.
- Repellent can go away after October 2.
- 14 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July, and check ND spray notices.
McHenry County against the rest of ND
McHenry County has the 16th longest season of 53 ND counties, at 151 days against 160 in Sheridan County and 135 in Rolette County. Its mean temperature is 41.1°F.
- Stutsman County: May 4 to October 3 (152 days, 20 WNV)
- Slope County: May 5 to October 5 (152 days, 0 WNV)
- Ward County: May 4 to October 2 (151 days, 35 WNV)
- Wells County: May 5 to October 3 (150 days, 5 WNV)
West Nile in McHenry County
From 1999 to 2025, CDC ArboNET counted 40 human West Nile cases in McHenry County (13 neuroinvasive) across 12 years. The worst was 2003 with 18; the latest was 2025.
See how the dates are worked out, and reading the West Nile counts.