Mosquito season in Knox County, NE: when it starts and ends

Mosquito months in Knox County

In a normal year mosquito season in Knox County, NE starts around April 20 and ends around October 16, about 26 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 Knox County, and when

• Start tipping out standing water weekly by April 6.
• Book any yard treatment for mid April, ahead of the July peak.
• Repellent can go away after October 16.
• 10 West Nile cases since 2016: you should wear EPA-registered repellent at dusk June to August, and check NE spray notices.

Knox County against the rest of NE

Knox County has the 46th longest season of 93 NE counties, at 179 days against 200 in Richardson County and 127 in Sioux County. Its mean temperature is 49°F.

• Dakota County: April 19 to October 16 (180 days, 3 WNV)
• Phelps County: April 21 to October 18 (180 days, 5 WNV)
• Madison County: April 20 to October 16 (179 days, 18 WNV)
• Sherman County: April 21 to October 17 (179 days, 2 WNV)

West Nile in Knox County

From 1999 to 2025, CDC ArboNET counted 38 human West Nile cases in Knox County (7 neuroinvasive) across 11 years. The worst was 2003 with 12; the latest was 2025.

See how the dates are worked out, and reading the West Nile counts.